Triss Merigold — After you save her you get the option to 'stay for a while...'. Note: If you do not select this dialogue option, you miss out on getting the recipe for the Cat potion at that point (assuming you chose to fight Savolla instead of the frightener). You do get that recipe regardless upon reaching the outskirts in Chapter I.
You can practice fist fighting with Eskel after giving the potion to Triss. Eskel can usually be found on the second floor wandering around, mostly in the armory.
You can get this only by choosing to fight the frightener. Afterwards, while you are getting the potion for Triss, talk to Vesemir and ask about arguing with Triss. He will give you a red meteorite after the conversation along with some other items.
Peasant Woman — Tulips can be either found on a corpse on the way to the southern Cave, bought from the Viziman herbalist, or given in exchange for any other 'gift type' flowers (daisies, roses, orchids) via one of the white-clad Townswomen in the western Outskirts. Give them to the blond Peasant Woman wearing the green and yellow outfit, roaming the main east-west road during the day.
Vesna — Save her from attackers outside the inn after 20:00. Agree to escort her to her grandmother's house; don't let her get killed. Ask to meet again, then bring a bottle of wine to the Old Mill Entrance (any Medium Alcohol will do) between 19:30 and 23:00.
Abigail — Just before the conclusion of Of Monsters and Men (once the Reverend has been warned to keep the streets clear), she will relocate from her hut to the southernmost Cave in the Outskirts; after Geralt travels there via the trapdoor in the Salamandra Hideout, she may offer herself to 'prove' that her reputation with the villagers is unjustified.
Zoltan Chivay — Get a set of dice off of various human remains (several drop from Racists); Zoltan will teach you how to play Dice Poker at the Inn (perhaps after Geralt shows these dice to other players below).
Barghest — 10× Barghest skulls for Abigail. Barghests attack randomly on the road at night.
Drowner — 3× Drowner brains for Reverend. Drowners can be found near the shoreline. Bestiary entry needed (e.g. by giving food to an "Old townswoman" in the main village area).
Ghoul — 3× Ghoul blood for Kalkstein. Ghouls can be found in the crypt and also along the road at night. Bestiary entry needed (e.g. by getting The Tome of Fear and Loathing, volume I from the Drunkard in the Outskirts' Inn).
Nadir —East of the Old Mill among Drowners. (It will only spawn after midnight and while Strangers in the Night is not active). Take its head to the Royal huntsman.
Ozzrel —Gain Mikul's trust by making a preliminary sweep of the Crypt; at this point there should be a second paragraph in the Crypt's Locations journal entry. The next time Geralt returns there, another corridor becomes available. Deeper inside you will find a larger, named ghoul, actually an Alghoul named Ozzrel. Take its head to the Royal huntsman.
Prostitutes — Can be found here and there. All give the same card. Can be 'bought' with flowers after the Working Girls Side-Quest, or before with money.
Half-elf — Enter the house across from the warehouse and obtain the "A Ghost Story" quest. She will be in the house across from Vivaldi's house after you complete it.
Gossip — She walks around and wants a pair of gloves or a diamond. A pair of gloves can be found in the Hospital.
Shani — After the party where you invite a friend, ask about the battle and make sure you have a red rose to offer her.
Morenn — Get the side-quest A Lost Lamb from Vaska. Bring her a wolf pelt and select the middle option (relieves stress).
Thaler — I used Kaedwenian Stout. Out-drink him and get a book called Shadow People, or the story of His Majesty's Secret Service, containing information on the Order of the Flaming Rose. Any kind of beer will do, but you need to be able to drink nine of them without passing out. His is the 'toughest' drinking contest, but also the most complimentary about your tolerance.
If you do get the previous book from Thaler, you can give this book to the Bootblack who will then give you the Prophet Lebioda's Signet Ring. This ring can be shown to Grandma to gain entry to Shani's room.
Messenger at the inn — Drink a beer with him you can sell salamandra badges to him, out drink him you get information about his boss who is paying for Salamandra brooches.
Yamo Ryeboozer, the boozer at The Hairy Bear — If you out-drink him, he tells you the recipe for Wives' Tears. As usual, beer is easiest. However, this only works if the Drunkard in Chapter I was not 'defeated' for a book; in this case, you can buy the Wives' Tears recipe (as part of a 'package deal') from one of the Lumberjacks in the Swamp Forest.
Thaler — He walks the streets or is in his shop across from the Hospital. (Professional). You can play him an unlimited number of times (a good way to make money for that Excellent Leather Jacket).
Alghoul — 3× Alghoul marrow for Kalkstein. Alghouls can be found in the cemetery areas. They can also be found at night in the swamp, eating the corpses. Beastiary entry needed.
Dog — 6× Dog tallow for gravedigger. Dog tallow can be harvested from Dogs, and can also be found in some of the houses in Vizima. Some merchants, like the Peasant Merchant near Shani's house, also sell dog tallow.
Drowned Dead — 10× Drowned Dead tongues for Siegfried. Drowned Dead can be found in the swamps. Beastiary entry needed.
Echinops — 3× echinops rootstocks for Gardener. Echinops can be found along the path in the swamps; one is outside the cave. (Beastiary entry needed; if you still have 3+ rootstocks from Chapter I they will suffice.)
Wolf — 10× Wolf pelts for Jean-Pierre. Wolves can be found just north of the Druid camp and also in the cave in the swamps.
Cockatrice — Killed in the sewers. It is a 'must do' quest.
Coccacidium — A very tough man-eating plant in the Swamps (looks like an Archespore but is much tougher). Can actually spawn in a few different places, but it is the same plant. Once you kill it, it will not spawn again.
Triss Merigold — Send Alvin to her, then chat with her and buy her a ring with rubies.
Shani — Send Alvin to her, then chat with her and bring her a silver amber ring.
Rozalind Pankiera (Lute Girl) — the girl you get the lute from for the bard Dandelion, either bribe or beat up her father to get to her. Note: you should first speak with Dandelion in The New Narakort inn and take the "Dandelion's Lute" quest from him, before speaking with Rozalind and taking the lute from the trunk in her room or you will miss her romance card AND the "Townsfolk" Journal entry!
Noblewoman — Stands in the street outside Triss' house near the jester, wants a Kikimore claw (they pop up at night). You can also click the option to give her money, then when the amount slider pops up, cancel it and she will say something about being treated like a prostitute and that you are a real man, then take you to bed.
Noblewoman — Wanders drunkenly around the bank, dressed all in white. Wants a silk scarf (gold shawl), which can be bought from the Peddler in the Temple Quarter. Giving her a scarf apparently negates getting the Kikimore-Claw Lady above, and vice versa.
Courtesans — 500 or a gem or a bottle of perfume (if you have the recipe) 300 if you outdrink Erkin von Blunt (three bottles of strong alcohol will do the trick, or 5 bottles of Sodden Mead). Note: their romance card is the same than the Blue Eyes' one BUT they give you the "Courtesans" Journal entry instead.
Princess Adda — after a short set of fed ex quests all in the same area at the party (no loading screen).
Queen of the Night — the climax of the Blue Eyes quest, if you choose one night with the sisters of mercy over killing the Lady of the Night. However, picking the bed with vampires leads automatically to a fight in which Order Knights will want a piece of you, too. If you wash your hands of the whole deal after the ménage-à-trois + one, also the vampires will be zooming in for a second bite.
Town Clerk — Diamond as a gift and she is all yours.
Dandelion — The New Narakort (only for fun/money, no XP until Chapter IV, or perhaps if you have played Koster).
Koster — Gamblers' den (on the alley along the walls — east of Maribor Gate, second house on the north side) (Sharper).
Note: Professional players will only play other professionals. If you have advanced past professional by beating 4 others, the remaining professional will not play you (e.g. You beat Thaler and Munro Bruys in Chapter II and Count Roderick de Wett and Velerad in Chapter III, the Hierophant will not play you. However, once the gamble icon is unlocked for a player, it remains unlocked even if you have advanced past their level. So, even if you advance past professional, you can still play professionals you have already beaten, just not professionals you have never played.
Archespore — 3× archespore juice for Jethro. Can be found in the Swamp (try along pathways at night). Bestiary entry needed.
Cockatrice — 5× cockatrice feathers for town scribe. Can be found in the Swamp, specifically the cave in the south. Bestiary entry needed.
Fleder — 3× fleder fangs for Velerad. Fleders can be found in the cemetary. There are many in the warehouse you can use to enter the bank (storyline). They also appear in the Swamp (at night).
Ghoul — 12× ghoul blood for Velerad. Ghouls can be found in the cemetary. They also appear in the Swamp (at night).
Graveir — 5× graveir bones for Velerad. Graveirs can be found in the cemetary. They also appear in the Swamp (at night).
Kikimore — 10× kikimore claws for Velerad. Kikimore claws are found in Kikimore worker loot. They can be found in the merchant area at night and also in the Swamp. Bestiary entry needed.
Wyvern — 3× wyvern meat for innkeeper. Wyvern can be found in the Swamp, mostly on the Wyvern Island in the north.
The Innkeeper at The New Narakort will divulge information about a password and also about another witcher who stayed at the Inn previously (presumably Berengar). With the second exchange, you receive Curses and the Cursed and The Book of the Kiss. If you bribe him a third time, and tell him that his information is not worth what you paid for it, he will also give you the formula for the Dragon's Dream bomb.
If the recipe for Wives' Tears is not available to Geralt, he can nevertheless obtain two potions from the waitress at the New Narakort for a pair of red gloves or 100 . Multiple conversations may be needed to trigger this particular dialogue. Interestingly enough, the same Waitress can also give you the formula for Devil's Puffball, just by talking to her and listening to her grandma stories.
Elf Woman — Bring her food (wyvern steak works nicely) in the elf cave. She is not Toruviel, she is wearing an elaborate headdress.
Lady of the Lake — After the hermit quest you get an option to tell her you want to go on a mission, tell her it was a jest after you say it.
Peasant Woman — Often hangs out at the inn or can also be found wandering around the village. A sugardoll is what she wants. White Honey to the baker gets the doll, or you can find them in various houses in the Trade Quarter and on many Salamandra (apparently their evil knows no bounds, and their diet reflects that). You can also obtain one by bribing the baker with a large sum of money after giving the peasant woman a different sweet item, such as candy.
Devourer — 10× Devourer Teeth for Witch. Bestiary entry needed. Can be found in the fields and on the Village map. If Abigail is the witch, she will also buy any extra devourer teeth you may have — but remember to keep one for the dentist in Chapter V).
Giant Centipede — 4× Centipede carapaces for the elven craftsman. Can be found mainly in the sw area of the Village map. Julian will buy extra chitinous carapaces off you as will the 'old hag' healer if you let Abigail get lynched in Chapter I.
Wyvern — 3× Wyvern Eggs for Innkeeper. Can be found on Black Tern Island and the fields.
Basilisk — 3× Basilisk Hides for Julian. Can be found on Black Tern Island. If Abigail is the witch, she will buy any extra hides off you as will the 'old hag' healer if you let Abigail get lynched in Chapter I.