Sniping is optimal, but go to your max with your last bid.
... but if you make this bid in the last few seconds, and make it your only bid, this increases your odds of 1) winning and 2) getting it cheaper if you do win over if you bid the same amount earlier. Sniping is optional, but it DOES increase your odds of winning and winning for less money. (Unless you forget to bid entirely or screw it up somehow, of course, but a sniping program will help with that.)
Another piece of advice -- don't bid an even amount. Instead, take an even amount, and add a bit more. Don't bid $150 -- bid $151.12. If two bids are equal, the earlier bid wins. So if you snipe at $150 and there was already a $150 bid -- you lost. And they might have actually followed the same rule, and bid $151, hence the extra few cents ...
No, No, No, never make a serious bid early; the system is far to open to abuse; make a nominal tactical bid by all means, but otherwise always save your big *** strategy for a last moment snipe; that's the only way to protect yourself from the unscrupulous shill-bidding vendors (and other naive nibble-bidding buyers). If you are a keen eBayer, as I am, and you don't have the time to snipe manually, get a sniping program.