What are the do's and don'ts in assembling computer?

1.Make sure the plug is removed, safety first!

2.Don't touch anything unless you are grounded

Static electricity can cause damage to electronics, according to howstuffworks:

The way you eliminate static elec tricity is by grounding yourself. There are lots of ways to ground yourself, but probably the easiest is to wear a grounding bracelet on your wrist. Then you connect the bracelet to something grounded (like a copper pipe or the center screw on a wall outlet's face plate). By connecting yourself to ground, you eliminate the possibility of static shock.