This has turned into a productive discussion. I think the posture of the person seeking help factors large in how I approach the situation. If it's obvious the person is just looking to steal some quick information, I do a lot of nodding and smiling and "good luck"ing. But if the person is genuinely interested in talking fishing, admits what they do and don't know, and is open to a little help, I'm more willing with information and flies.
For example, I remember a few years ago meeting a guy on the stream who clearly didn't know what he was doing. Initially, he nearly waded up on me (probably former spin-fishing habit) and I was a little annoyed. But then he watched me quietly for a minute and said, "Hey, I just started doing this, and I don't know the first thing about it. Would you mind giving me a few pointers?" A great opening line that beginners would be wise to memorize. I proceeded to sit down with the guy on the bank for 10 minutes, showing him how to tie a few necessary knots and in the process tying up for him a suitable leader. As we sat, I explained to him the general theory behind nymphing (that fine balance between dead-drifting and line control). We then fished the rest of the run together, after which he said thank you and I said you're welcome and we went our separate ways. It took me a half hour to teach this guy what would have taken him years to learn on his own, and I was happy to do it because of his teachable attitude. Unfortunately, though, people like that are the exception rather than the rule.
Lest this story lead readers to believe I am a fountain of goodwill, though, let me assure you that I tend to be pretty secretive by nature. The irony is that, when Phil questioned Matt's response about his flies, I was thinking similarly but along opposite lines - as someone who fishes the Little J., I was a little perturbed that Matt would post rather detailed stream information about it on a public forum. Now I don't fish it enough to be fiercely protective of "my" spots, and it's a huge stream that isn't really at risk of being overfished because of a few online comments, but in Central PA we see enough pressure, and I always hate to see information shared publicly about its streams. It's a bit of an awkward situation, though, because when people help you out you'd like to let them know how things turned out. But my personal preference would be to keep these kinds of reports to PMs.
-Shawn