Do you tend to give other people the benefit of the doubt and take them at face value until they prove themselves untrustworthy?

I used to be quite the cynic, but, then I started to assume that most people were generally decent types who spoke their minds. However, I'm coming to the conclusion that a much more guarded approach is necessary these days.

It's a pity as I'm no great fan of jaded/glass half empty people.

Anyway, what do you think, do you assume that those you meet are genuine initially or do you hold back until you can establish their true character?