My preference is to listen or view before I buy - especially in the case of speakers, but sometimes it may not be possible as a manufacturer may not be in the area of where a person lives. In that case, the best bet is to reach a reputable online company/dealer that has an excellent return policy.
Notwithstanding the above, I have had success on Audiogon even though, in most cases, one may not receive a factory warranty on a purchase.
One other point - with smart phones and tablets, it's easy to comparison shop in a brick-and-mortar store like Best Buy or HHGregg.