I use ebay to mainly buy clothes, wigs, accessories and collectibles so I only have experience from those kind of sellers. My purchase went really well and that is probably thanks to my 'ebay routines'. I always check the bad ratings of the seller first. Why? Sometimes a seller may have a loooot of good ratings so that the bad ones disappear in the crowd. Look them up, read why they were unhappy with the purchase and then consider if you still can trust the seller. Maybe it was just a problem with longer waiting time for a customer or it could be something more serious that you are scared of happening to you.
I also have my own principle when purchasing anything on ebay: never buy expensive things. Why? Actually it LIMITS the chances of me being scammed of a ton of money for possible $#*!. Also, I am on the internet to find lower prices, not higher than in stores. Then of course, if it is ridiculously cheap then always consider why that can be the case.
Lastly, if it is something that has a high risk of being fake (collector's objects or alike), then it is good to try and contact the seller for more pictures. If you get no answer maybe he is unavailable or just ignores it all together for reasons we fear. If he agrees it is good if you ask the seller to put something in the picture that normally would not be included so you know that the picture is genuine. Maybe a bottle or a cup, an item everyone has but would not normally be included in photos on the internet so that he can just copy it and send it to you.
Sometimes we can get into contact with scumbags on ebay. But several times it is just a seller who wants to sell GOOD items and get nice reviews to help his business further.