Horseshoes' advice is excellent, as are the others. I've been a member since 2004.
If you're new to EBay, I would first try and buy a couple of smallish items and get a couple of positive feedbacks. You'll get a good idea of what to expect when completing the transaction. When you receive the goods safely, don't forget to leave good feedback.
When selling items, it's often a good idea first to look for a similar item for sale. If it is, then see what is being asked for it in 'BIN' Buy it Now, or wait to see what it actually goes for, if on auction.
If the goods are collected from you, it's got to be cash only and you should insist on a copy of the invoice you sent the buyer which should be presented to you on collection. This is to ensure the right person is actually picking the goods up from you. You should also have a printed copy of the invoice. The buyer signs one to give to you, saying they've received the goods and you sign yours to give to them saying you've received payment.
Job done! If they pay via PayPal before picking up the goods, then refund them immediately, insisting they honour the agreement of cash on collection. This would have been spelt out in your description and terms.
I've only had one negative feedback and this was given to me before the buyer approached me to sort out the problem. I told the buyer that was not the way to do things on EBay. I gave him an immediate refund and he withdrew the negative feedback. That's why EBay will usually side with the buyer, because it's they who withdraw the negative feedback, not EBay.
Good luck with your sales.
If you're interested in photographs, look at an item I'm selling. 122297276103