depends on how much you want it.
if you really want it then wait till the end type in $20 higher than what it currently is, then with 1 minute to 30 seconds to go type another 10, while watching if it is going up if it is, someone else wants it just as bad type in 20-50 more by the time they realise whats going on you win!!
works for me every time, i very rarely lose many auctions these days , you sometimes have to pay alot, but like i said how bad do you want it, if someone else wants it you are going to pay alot anyway.
trust me it works