Hi Karen,
The setup to sell is easy-they talk you through it pretty thoroughly (sp?). I did all the tutorials and read all the books I could from the library. Ones I recommend are Ebay Hacks (tips and tricks you won't find in tutorials etc.) and Ebay for Dummies.
Research is the key though. I started off clearing out old junk from the house. It got to the point where if someone couldn't find something they asked if I'd sold it
Now mostly I find good deals in stores. My sales go in cycles. 1 week nothing sells, then another most everything goes.
When I find new items to sell I do a search and a completed search too (very important) to see what has been successful (or not), popular opening bids, how things were listed etc. Oh and don't forget to search through the stores too. A lot of people - me included- put stuff in there that doesn't go the first time around. You can have stuff in the store for 30 days or more.
As for postage, I used to guess and sometimes came up short. Santa brought me a postal scale for Christmas.
I'm rambling sorry, there's lots more to tell I just can't think of it all now. I consider this my PT job now
and am on all the time.