Lots of people (including me) like to bid at the last minute. But it is not essential, because as nattyclare has said, you can just enter the maximum you would like to pay, and go away and leave it until the auction has ended.
If the auction starts at 99p, and you decide that the most you want to pay is £5, then you bid £5. If no-one else bids, then you will get it for 99p. If other people bid on the item, then eBay will go on bidding for you, up to your maximum of £5.
Actually, it is a good idea to put in a slightly odd amount - I usually put in something like £5.56 as my maximum bid. Lots of people bid in round sums, to the nearest pound or 50p, so the extra couple of pence might be enough to win.
There is always a chance that someone will outbid you, but that happens even if you do bid at the last minute!