A good designed site and rich content site worth a click always, I always click on ads if I like the site, but only that way.
For my own site, never. If i see something I interested in, i try and find it on google. For other plls site, ocassionally i find interesting things such as free blogs, hosting offers and traffic marketing.
My own ads - never. Other ads on other websites - I click when I think something is of interest to me although being a webmaster myself, I tend to be a little more careful about what I click on since I know it costs the advertiser money.
i click on a google ad when i am a lot curious about that! never clicked my own ads (after the first month when i had got it)
Only when I see something intresting. If I don't like the site where that ad is I don't click even intresting ads.