Which one? there are 3 levels that have snow but i'll take a guess at Hoth. If you are playing as the Empire get into the AT-AT and stick as close as possible to the other one so it is harder for snowspeeders to get you, then destroy the sheild generator and move onto the hanger and capture that and the other command posts along that route. This tatic has yet to fail me. I haven't really got a strategy for playing as the rebels.
I haven't used cheats so i can't say if they work or not.
Let me be the first to congratulate you on witnessing pure perfection!