If your using a dexxer its pretty easy
Set 4 hotkeys
1. drink explosion potion
2. last target
3. set last target(or you can do hotkeys for "target closest murderer, target closest innocent, target closest enemy, target closest gray. I hate hotkeys for all 5)
5. clear target queue
So....you see someone you want to fight
First, always hit "clear target queue", this will make sure you throw it where you want
Hit set last target, and click the dude you want to fight. If you have a "target closest X" hotkey, its a bit easier since you don't have to actuay click them first
Hit your "drink explosion potion" hotkey
The countdown will begin.
Hit your "last target" hotkey to throw the potion
The key is to throw the potion EXACTLY at 2.0 seconds. RIGHT before the the 2 changes to 1. If you throw the potion right when the 3 turns into 2, thats way too early, and any moving opponent will easily evade.
If you throw it anytime the counter says 1, the potion will explode in your hand, damaging YOU
If you get STUNNED while the countdown is going, its a good idea alot of times to click the ground anywhere away from you, as a wise opponent wiil stand next to you so your potion hurts you as well. That's right. If you are too close to your target when it explodes, you get hit as well
Also I should add: the server changed it so you can throw potions in towns. Before, the potions would hit anything closeby and result in you getting guardwacked. That's not the case now
Good luck