Now, there really isn't an all powerful law when it comes to busking ethics, but here is a few rules that I learned when I play in NJ, or NYC.
> Never spend more than an hour or two at a pitch
In a lot of places, there is always a few sweet spots, but hogging the same place for 3-4 hours doesn't make it fair to other buskers, so I tend to change places every hour or so.
> Keep at least 50 feet away from other buskers
Depending on the instrument, some make A LOT of noise (ex. Drumset, Acoustic guitar, Electric guitar, Banjo...) so you want to keep some space between you and other buskers so that your performance doesn't drown out theirs. And regardless of what instrument you play, If another busker is around, don't make more noise in an attempt to make them leave. It makes you look like a %&#@head and it's childish.
> Pitches are first come, first served
Before you or someone else gets all butthurt because "Your Spot" is occupied, Remember the universal rule "First come, first served." Neither you, or anyone else has a clam on a specific spot. So if that spot is taken, find another one. Don't act like a child, Please don't...
And remember "People are like assholes, everyone has one". So if someone throws you a dirty look, just smile and wave!
Anything I missed? Feel free to add.