Guide How To Grind As An Assassin/ninja

First of all, pick a good grind spot. If any enemies have projectiles, it's the wrong grind spot.
You want to have enemies with predictable AI, that will just follow you around mindlessly.
Step 1
Vanish into the middle of the grind spot. Then unvanish, and have the enemies follow you around.
Step 2
Once you've got a sizeable group coming after you, start hitting them. Maybe a few smoke bombs, but if you don't have any mana regen, use primarily your main attack. Enemies will die and respawn, letting you keep the mob of mobs roughly the size it is at all times. Do this until you've reached your XP goal.
Spells
Use the spells as panic buttons. If you feel like the mobs are starting to get out of control, Spin Attack, then Multihit them to get them back together. If you've completely lost control, mobs surrounding you, no hope left, Vanish, get out of there, and start over.
And that concludes my master tutorial of Assassin grinding!

 

How to grind as any class: Find a spot with a good spawn rate/xp ratio and start killing stuff

 

And also if you have manasteal and the mobs are tankier just spam smoke bomb and hit them from time to time. Slows them and does good crowd damage

 

Yeah, I always do that.