A knowledgeable buyer is a wise one. And you won't lose much money either. Before buying stamps, educate yourself about centering, faults, fakes, etc and what does catalog value really mean.
There are online sellers who are wonderful people
, some who don't know anything about stamps
and unfortunately there are also many scoundrels
If you have other DOs & DON'Ts, please feel free to post yours. I'm sure I missed some.
--Check sellers feedback, S&H charges, return policy (especially for
high catalog value stamps) and payment options.
--Read the description CAREFULLY. Ask questions if you have any
--Capture a photo of the stamp and enlarge it on you computer to
check for faults and types that may not be described.
--If the Scott number is given, do a search to see how much other
sellers are selling it for.
--Assume the description is correct.
--Assume that the stated catalog value is accurate.
--Buy items with poor quality photo images.
--Buy questionable stamps unless you are willing to lose money if it
turns out to not be was you had hoped.