I'm a new rider, although I've spent a lot of time looking up proper techniques for spinning, shifting, etc. I do appreciate any advice which will help enhance my ride in either terms of quality or performance. I don't get passed by a lot of cyclists (perhaps it is just where I'm riding) and if anyone passes, it's usually me (now that I said that, I'm going to get destroyed), but it would be really easy to sound condescending if a passing cyclist offered some advice - especially if they got out of the saddle to get back to their original pace. If a good cyclist passes me, he/she needs not to speak. I'll most likely analyze how they're form looks and try to compare myself and see what I should or should not change.
That being said, when we're in the group ride, I do ask a lot of questions at the start and then settle in and try to watch and learn. If I look a bit concerned, the cyclist next to me might mention some tip or advice, but that's about the only time I appreciate randomly offered advice on a ride.