Normally I will use EtOAc/Hexane. If that does not separate the mixture effectively, I will try other combinations:
Strong solvents: EtOAc, acetone, diethyl ether
Weak solvents: Hexane, toluene, DCM, CHCl3
This week I've run columns in acetone/hexane, EtOAc/chloroform, EtOAc/Toluene, and EtOAc/hexane. The project I'm working on generates products that tend to co-elute with the starting material in most solvent systems, so I have to get creative.