it's up to you. your favorite is the best for you. loose tensions are faster but the cube may lock up. tight tension is slower but the cube is more easily controlled. there is no right way to do it.
I use a dayan lunhui cube: http://www.icubemart.com/apps/webstore/ ... ow/2309063
with CRC lubricant: http://www.amazon.com/CRC-05074-Silicon ... 932&sr=8-3
my cube is tensioned to a medium setting