Rule#1 Don't be cocky and tell yourself....yeah I'll remember this goes there.
Rule#2 Get the manual
Rule#3 Pay Attention
Rule#4 Take your time.

With that said. What I usually do before any teardown is to photograph the game from a million angles before taking one thing off. I do the same thing for inside the backbox and make sure you take picture with the ribbons on and off. Sometimes the ribbons block some conenctors and you can't tell which one goes where. With time you won't need to but for starters make sure you have good shots.

Next up Take the part out and take a picture of it assemble on many angles if you have to. Take the piece apart and photograph all the pieces neatly laid out.

Now here comes the part if you are comfortable of not. You can either ziploc the parts of one mech all together or split it up in categories like washers, nuts, bolts, springs etc and then rely on the book to reassemble or once you have labelled everything and put every mech in their individual bag is to go bag by bag and clean part by part.

I've learned from my mistakes and what I have done now is that I put all the screws, nuts, springs, items that are the same for the entire machine together and label them properly (all the 10-120 springs are together. You'll kick your own ass at reassembly trying to figure out if that is the right spring. I do it this way because it's easy to put a whole bunch of stuff in the tumbler at once. So when I am ready to tumble I put 10-120 springs and let's say hex bolts togther..that way I don't get confused has to which spring it is that I am pulling out of the tumbler. In other words i don't put two of the same things in the tumbler at the same time. So washers x will not go in with washer y.

And do yourself a favour and get Blitz tumbling media and so high grit medium...so small grit takes forever to make a part shinny.