It can be done either manually or by using a software. The first one is the safest thing to do but it is not very easy. You need to make note of date and time the bidding ends. Remember that sniping is against the eBay rules. So make sure you are logged into the auction by about thirty or forty five minutes before the auction ends so that it is not considered as sniping.
You can open up two windows, one to watch the current status of the bidding and the other one to place your bid. The objective is to make sure that you are not outbid by a sniper or to bid higher than the highest bid during the last few seconds of the auction. But this is a difficust task as there are softwares to do this automatically and they will do this in just seconds.
The another method of sniping is to use a sniping service found online. You can also purchase a software which is specifically designed for that purpose. These softwares can be found online and they are relatively inexpensive. There are some good ones listed at salehoo review What you need to do is tell your software which auction you would like to bid on and what is the maximum amount you wish to pay for it. The software will automatically monitor the auction and snipe it ensuring you your success. But this is against the eBay rules and when eBay enforces this rule you might be banned.
Sniping is very bad if someone does it for you, but if you do sniping by yourself to win bids then it can be a wonderful thing.