Prepare gel box:
Clean gel box and combs etc with detergent, then dionized water.
Then incubate the gel box and components in 10% H2O2 (hydrogen peroxide, stored in cold room) for 30 minutes.
Rinse box thoroughly with DEPC water.
For making gel and preparing samples:
Your should pour (and ideally run) the gel in the hood, since the gel contains formaldehyde. [see protocol from Maniatis (original edition)—attached.]