I recently spun a pretty rare Phish show for a cool guy who is running a tree of it. No questions asked, it's done. So, when you do grovel be keen, maintain etiquette and remember that this person will be doing you a huge favor in spinning blanks so make sure to be kind in return in one way or another. First off, it's great experience and secondly it will help you build your collection. Again, even if you don't think you're going to like the band a lot, it's a trade.
People love seeing masters on people's lists.
One, I get the exact equipment used. Two, less chance of errors. Three, tapers are great resources. They know stuff. Offer a service for DAT clones.