When you first get it you will do a seasoning run - without meat. You want to leave that seasoning coating everything on the inside - this is what prevents rust. Right after you pull the meat off of the smoker lightly hit the grates with a grill brush to get any heavy junk, but don't scrub so hard that you remove the seasoning.
I line the bottom of mine lengthwise with 3 lengths of heavy foil (Costco roll). If you start at the bottom and work your way up the pieces will overlap like shingles on a roof. Then after each use you just wait for it to cool and roll up the foil with 98% of the grease and toss it. A few paper towels will clean up any remaining grease.
Other than that I just empty the ash tray once everything is stone cold and use a hand brush to sweep out the bottom of the fire box. And once in a while I hit the outside with my pressure washer to clean the dust and dirt.
Oh... my tuning plate is the grill pan in the main chamber flipped over an hung on it's highest setting. So I cover the top of it with foil and toss the foil with the rest of it.
I'm sure some other folks will have some good sugestions to. You will like the Char-griller, it's great for learning fire controll and makes some really good Que!