It's the first time I'm bidding on eBay, do you have any experiences that I should know?

I'm bidding on eBay for the first time on 3 items, and they're from pretty reliable sellers...

i'm bidding on stuff that i'm currently winning the bid and there's like 2 days left. i really hope that i'll win the bid without someone raising it in the last minute -- does this usually happen during the last few hours of the bid?

so I guess I have to pay by paypal but is that safe? and how do I tell the seller that i've paid? do I just send him the message and my shipment address?

what do I do if I haven't received my stuff in the time the seller promised?

anything else important?

thank you.