We wrote this walkthrough using version 1.31 of the GOTY edition of the game. We also used the Story and Sword difficulty.
The walkthrough only includes pages for quests that appear in your journal. Other quest-like interactions are covered on the location pages.
In the walkthrough, we list the default experience points awarded during quests. But the higher your level is over the quest's level, the less you'll actually receive.
Bombs, potions and oils work a little differently than in other games. Instead of consuming them when you use them, they have charges, and using them just removes a charge. Then meditation replenishes the charges (provided you have a strong alcohol like
available). So you only need to craft each bomb / potion / oil once.
Each time you level up, you gain an ability point. You also gain ability points from Places of Power. You can spend these points to build up your abilities, but only the abilities you place on the right side of the Character screen actually benefit you. So you might end up with more abilities than you can use, and have to swap them in and out when appropriate.
For "horse equipment," blinders and saddles only help your horse (aka Roach), while saddlebags and trophies help you. You receive your horse equipment bonuses whether you're using your horse or not.
You can't use signs or melee weapons while swimming. In that situation, you can only use your crossbow.
To examine your gwent cards, bring up the main menu (by pressing escape on the PC) and select "Gwent Deck." There are multiple gwent decks, and you can choose which one you use when you play somebody.
If you approach a shopkeeper and you don't get an interface option to talk to him, then just save and load your game. The interface option should come back.
Corpses (including destroyed monster nests) disappear when you load your game. So always loot first and then save.