2) keep track of the screws, and where you removed them from. Don't mix the screws from the front of your case with the ones from the back of it. The ones that go on the back (by the ports) are a little longer, and you'll dimple the plastic below your keyboard if you use the wrong screws!
5) make sure the keyboard is properly lined up before snapping and screwing it all together. nothing is more annoying than thinking you're done, only to realize your escape key is sticking on the plastic case. ;-)
Ah I learned these things from all those fun hours playing with my A1200 over recent years.
Such fantastic machines, don't make them any rarer by breaking them!