I park mine in the shop to dry off and go over it with a whisk brush. This gets most of the dirt and crud.
Next I wipe it down with a damp towel. this gets most of the non-oil based crud.
For the oily stuff I use a rag with a little diesel on it, then wipe off the residue.
Every couple months I remove the chain and rear derailleur for a proper clean and lube.