Is there a great place that you can easily pull mobs to compare weapon/spell combinations? What's the best way to do this comparison, do a single hit and see what kind of damage it does?
Aside from practical experiments, you can also do some theoretical study using Blizzard's skill calculator here, and if you want to play it safe early on and choose only combinations of skills that are generally useful together, you should use "non-elective" mode for selecting skills.
The details are explained in the below video.
the best ways are on traps kind. like the one below. But you can also go for Jar of souls. those are the best places in ACT I.
This is the best place in my opnion.
PS: There is an trap too that is hard to find, but really good. I wouldn't go for it, but instead for the second video.