Can't speak for others, but I only tip the $20 at Christmas. The rest of the year it's $3 to $5.

No doorman for me, either. And tipping like this isn't strictly bound to NYC. Same goes for the 'burbs.

As for tipping other folks, like a personal trainer, I have found that such a gesture pays big dividends the following year - usually in the form of a free session or generally better service (maybe some training when we're not actually scheduled for a session but just happen to be working out at the same time). Same with the golf instructor. I generally find that I get at least what I give in the long run.