For general cleaning duties I use Dawn dishwashing soap, a bucket of hot water, and brushes with natural bristles. Rinse gently and towel dry. Now, if the drivetrain is really gross, I remove the chain and clean it in the appropriate solvent/degreaser (usually mineral spirits). With the chain off I'll clean the cogs and chainrings with something like WD-40 Bike cleaner/degreaser, but diluted citrus degreaser is fine, too.