Depends on what your running. I assume your character is a sorc, most likely cold or fire.
First thing you need to do is clear the area of all the council members and vampires. This way you don't get into deep trouble. Tele to Meph and lead him over to the gap by the act 4 portal. If you look closely their is a set of steps on the left or right leading into this gap. Get Meph as close as possible to the edge there. Tele across the gap walk about a quarter of the way away from Meph, ( just enough that he will be able to click on for an attack) and launch your most powerful spell at him ( meteor, blizard, orb) All of Mephs attacks will cross over the barrier, but if you are far enough it wont touch you. Spam the skill till he dies.
Word of advice, don't try the moat trick with a merc, it will die if not strong enough.
Good place to MF at any lvl is in act 1 pits (in totem highlands area) also from personal oppinion, I would suggest about 230-250 mf
if your looking for a SoJ try norm Andy runs, for me they seem to drop their the most