Show up early! Many of the stores that have massive sales will sell out fast. The whole purpose of having super cheap items is to get people in the door.
Spend some time before the big day to make a list of people who you will be shopping for. Next to their name, include a budget and a gift idea. Make sure you keep this list handy while you are strolling through the stores.
Make a list of specific items that you MUST have from the ads. Most black Friday advertisements come out on Thanksgiving day. As you browse through the paper, circle the items that you think will sell out and grab those first thing in the morning.
Keep an eye on the prices of items that are not on sale. Many times these items will be overpriced to compensate for the super cheap advertised items.