Having just read a blog by a guy who sent some goods to Nigeria before getting payment, I am going to write this in the hope that at least one person will avoid being ripped off.
NEVER NEVER NEVER and also NEVER send your goods out before recieving payment. It is also worth remembering that some countries have either corrupt governments or leaders who have got bigger things to worry about over ebay cons. Africa has many nice people in it, but there are also alot of desperate and/or immoral people there (famine has that effect). If conning people on ebay was the only way I could feed my family, I'd do it.
Honest people will for the most part not be paranoid about being ripped off and will be happy to hand over their cash prior to you sending the goods and for extra safety, use paypal. When I sell, I only use Paypal and I only buy from ebay sellers using paypal. I have only ever purchased something from a non-paypal user once and I got ripped off. Paypal's charges maybe higher than some similar payment methods, but if you go by the old adage, 'you pay for what you get' and 'if it sounds to good to be true, it probably is' then you will probably be okay.
Also if a buyer has good feedback, but only has a few ratings. Read them. Many people are charitable to new ebay users and will give good feedback, but make a few constructive remarks within the feedback comments, this may help you decide whether you want to deal with them.
If you have a bad experience with a buyer you can also ban them from further purchases by putting a block on there user ID as well as putting in a complaint.
For the safety of other users, always report dodgy customers so ebay can kick them off the site.
When selling items, state your terms and conditions clearly on the main page (not the daft little box at the bottom in the traditional small print type that nobody reads. Even if you put things in there you can end up with Negative feedback by lazy eyed people accusing you of not saying something, when it is quite clearly stated down there). Use a good sized font, a different colour to your main description and a different style often helps. Someone who has a well set up page and oozes experience is less likely to attract con-artists. Look at other peoples terms and conditions to get an idea what to put on there, but remember to put important things and things that could result in Negative feedback first or clearly caterogize them, remember most shoppers don't want to spend the afternoon reading pages of terms and conditions.
Professional language when dealing with Negative feedback is also important. Flippant remarks and name calling only hurts your reputation and/or character. This is another thing con-artists may pick up on. Someone who speaks like a professional is less likely to be targeted. If someone leaves you unfair or abusive/threatening feedback, complain to ebay. People like that will usually slip up often enough and end up being booted off ebay.
This is by no means a comprehensive guide and I highly recomend studying all ebays selling instruction pages (printing off a hardcopy and keeping it by the computer helps).
Hope this helps.