The biggest thing to remember I have found is to:
Decide exactly the higest amount of $ you will pay for that item. Bid that on the AS. Then just decide that if someone wants to pay more, at least I did not over pay. Another one of those things will show up again.
Also, If I really want something. I will research on Ebay that item's past sales price. I will also check on the open web for that items retail price. Then I will know what the max I will pay for it.
Also, I agree with Mrs. M. The ability to cancel your bid if you find something better is worth its weight.