How do you buy signed stuff with confidence?

[Veggz]

Hey!

Seen a lot of signed gaming items for sale and I see many on the forum own signed items.
Everytime I see a poster etc. that's signed I'm constantly thinking about the chances of it beeing fake, and therefor always skip it.
I would just sit all day and stare at my newly purchase thinking ''did I just get screwed over.''

Only signed item I have is Uncharted 3 drakes journal hardcover limited to 500, where I know all the 500 were signed by Nolan

I just wonder how do you buy signed items without having this shitty feeling?
Do you just trust the seller, do you have someone looking at the autograph etc? Thanks in advance!