I used to be very active, now occasionally.
Number one rule for buying: Never bid early, never incite interest in an item. Work with at least two browser pages open on the same auction in case one stalls on you. Wait for the last minute, but before hand decide 1) I really want this or 2) If there are many auctions for the item and you want lowest price, willing to make multiple stabs at it.
For choice 1- in a single bid, but the highest your willing to pay, with 45 seconds left. If someone tries to notch it up a dollar at a time, you'll win it. If they put in their max bid, then the one willing to pay the most wins.
For choice 2 start a couple of minutes early and do smaller bids, hoping for a deal, but realizing you might run out of time. Make your last bid the big one if you really want it.