Well, specifically grinding for skills is the same for all classes.
There's only few options:
- The easy way: put some arrow on lvl 9 (I use that a lot anyway, for luring or as finisher, or farming, or whatever). Go to a place with a decent amount of monsters that don't hurt you and not too many other people around. Hold down the arrow key and click on monsters to kill them.
- Combo: basically the same, but with using combo. You might need two skills for this, and it requires a lot of concentration.
I always tried to combine the first "method" with farming for alchemy materials, so I was going for monsters dropping whatever I needed (Aramid, for the most part, then Bluestin and/or lvl 2 items). Makes it a tiny but less boring.