Here are my TOP TEN TIPS
Over the past year I've bought substantial amounts of stamps from various sources but an awful lot via eBay.
As a result I can offer the following top tips...
1) Avoid buying if there's a fuzzy picture, if it's doesn't look right, it probably won't be right - you've got to see exactly what you're getting.
2) If buying collections, you can be 100% certain that someone has been through it with a catalogue and a magnifying glass regardless of what the listing might say.
3) If the stamp collection is local (or even if it's not) ask if you can see it before bidding, most people will say yes and you won't get a nasty surprise.
4) Check to see if the seller offers a money back guarantee if their description is wrong, most good dealers/sellers will offer this.
5) Condition is everything with stamps, it really isn't worth buying space fillers unless you've just started-out or are on reduced budget, always buy the best you can afford.
6) Be aware that the imperforate stamps and official overprints get forged - a lot. Best to buy from a seller with a high rating - they should know what they're selling.
7) If you're spending serious money on a stamp, ask the seller to email you detailed scans of the front and back - it always pays.
8) Why pay more for unmounted mint? How often are you going to look at the back? Mounted mint is just as good in my opinion for a standard collection.
9) A substantial number of buyers use proxy bidding systems, you ought to have one too - it stops sellers using third parties to bid-up the prices (I've seen this happen a lot).
10) No matter how rare the stamp is being sold, just wait a few days and there will be another one along!
11) Collecting postmarks doesn't make you a bad person (although it's best not to mention it at dinner parties)