I never bid on an auction until the last 10 seconds or so.
There's no point placing a bid earlier - all you're doing is driving the price up and will 9 times out of 10 be outbid anyway.
You have to decide the max you're willing to pay, and bid exactly $0.01 more (just incase your high bid happens to be the maximum bid of the current winning bidder, so you still outbid him but dont have to pay any more), about 10-15 seconds before the end of the auction (so nobody else has time to bid). Commonly known as "sniping".
The only problem with this is that everybody does it now so if it's a popular item you end up with 10 people all bidding in the dying seconds.
As a seller it's quite amusing to see something you're selling stay at $50 for the whole week then shoot up to $200 in the last 30 seconds :-)