I went with "Innocent until". I haven't been doing this nearly as long as most of you so I don't have enough experience to identify a forgery. So, I try to purchase from the most reputable sellers that I can find.
As far as online vendors the majority of my purchases have been from
APMEX. They are a big company and have a very good reputation. I have never received a coin from them that I had reason to doubt.
On
ebay I only buy from sellers that have tens of thousands of transactions and a 98% or higher rating.
None of my coins will ever be sold because they will be handed down to my children. If there are any forgeries in my collection I will never know about it.

My American Silver Eagle collection
http://goccf.com/t/448125My random silver coin collection
http://goccf.com/t/449270