Acordin to my experienxe,nightmare have a good chance to drop certain items but i never did it like a pro,only few runs as everyone for travwling to hell mode .
My questions is whats the best areas to play for mf in nightmare , whats best lvl range , and whats the character to do with?
thanks

You've posted this as D2, not D2R .. so i will answer in that fashion.

I personally start every ladder season with two characters .. i run one ahead, leave the game, and run the path taking waypoints with the other. I do this in a zig-zag mode, so to say, level one up, plow ahead, then level the other. I start quest bugging diablo in normal, leveling one, then baalruns in normal, leveling the other.

As to your question, i do the same in nightmare. I've just done so, and am quest bugging nightmare baal at this moment, leveling the other assassin. I think those two bosses, diablo and baal, are worth quest bugging and running.

But in terms of running just to run areas....i think it is always better to run act 1 hell instead of any act or area in nightmare.

i do same as you do sometimes. YEs , act 1 hell is much better then any area in nm but as i experienced , some items like charms and some jewels are most likely to be drop in nm . thats ahy i would like to try out . anyway .. ill do as my own if there is not a guilde already .