open the trade window with someone, open your recipe book, drag from the picture of the teachable recipe into the trade window. edit: this also works for emotes.
yes I can. ok your recipe book is the 'b' key. So open it and then open up a trade with someone by right clicking on their character. Look at the picture icons of each recipe that is what you will be dragging to the trade window. If the recipe says teachable or re-teachable then you can trade it to other players and vice versa. edit Alley beat me to it.
yes. and it's always worth checking which is which: i've seen people selling 250-gold npc recipes for thousands.
Players don't generally sell the recipes you get from the vendors unless it was a convenience thing. You will find that most players are very happy to trade what they can. I know I am. But beware it takes time to trade all the recipes some of us have. You can only fill the trade window page and then you have to accept it to open another trade window and keep doing that all through the recipe book. There is no quick way to do it. If you would like hit me up in game I'd be happy to share; I'm Majoria .
It is worth buying all NPC recipes, in the crafting profession you wish to master, that are listed as "Not Teachable."
Agreed, and before buying any that say "Teachable" or "Re-Teachable", ask your friends if they have that one already and see if they will trade it to you.