You will have to try it out. Just target a NPC, then type /train
The skill window will pop up with the stats in it that this NPC can teach you, or, if the NPC can\'t teach you anything, it\'ll tell you \"this person is not a trainer\".
Select the skill you want to train, then click on the train button (upper part of the skill window).
Once you have learnt 100% of the theoretical part of a skill (within a level) and you use the skill, you will advance in the practical part, until you level it up. Then, you have to redo the procedure to advance to the next level.
I hope that was of some help.
