I hear a lot of talk about snipping always wins the auction but this isn't always the case! What I've found is that certain auctions deserve a certain tactic and the same tactic will not always work on certain items.
The first thing you must always do on Ebay is research your item. The questions you should be asking yourself is what price would I be able to purchase the item off eBay at a retailers site. What price has similar items gone for in the past on eBay, how many bidders has there been on previous auctions, has previous items gone unsold, what price is a 12 month guarantee you'd get at a retail website?
Firstly you should always research your item, check with comparison websites for the lowest price, find out if there's various models and find out if there's any difference between releases. In the past I've been looking at Axis 7000 scan servers and seen ebayers post auctions claiming that these are worth at least £700 but infact they have a release 1 model which is probably only worth double figures if not less!
On previous auctions you should be looking at the final price sold to give you a idea of what you might have to pay. Next have a look at the previous bidders, is there a couple of bidders that have been trying to obtain that item? Do these bidders always snipe with exactly the same value bid every time! :-) Is there a eBay store that purchases most items below a certain price and resales them higher?
Finally choose your bidding tactic, I've found that on some items that are extremely popular and the availability of the item is high an earlier bid near the typical ebay sale value will often beat a snipe. Now if you've bid correctly near the end of the auction two things can happen, if there's been no bidding war the sniper can underestimate your bid and won't even come near the mark. Whereas if their has been a bidding war they've now left with the choice of not bidding or sniping you and ending up paying the highest price ever on eBay!
The less popular items I've found are probably best sniped at the last minute, don't snipe what you would for a item that doesn't get listed on eBay that often, if there's been loads of unsold items your going to be the only bidder on a auction sooner or later!
As for the rarer items on eBay these have to be sniped, you can guarantee there's going to be no guide to the typical selling price, but keep in mind the items actual value since I've even been sniped and had people snipe on my auctions for values far in excess either what I've paid for the item or what I could purchase one for!
Personally I don't like snipping, as a seller you don't know who is going to bid on your auction until the last second and as a buyer unless you use a sniping service you have to be at a computer at a certain time. I've also found that snipping services are not always accurate, you can't fully judge what tactic you should use and your giving your ebay details to a third party. I've also found that by judging the processing delay between yourself and eBay it's very easy to out snipe these automatic services.
I think it would make eBay better if eBay added a hidden bid that only was only visible by the seller but only take effect when the auction just closed. Add the feature to restrict new bids without permission from the seller before a certain time and then everybody would have the option to snipe at zero seconds and the seller would get protection from bidders they don't want to have bidding.