I haven't busked for years, but here are some tips for buskers from my experience:
-Women buskers seem to make more than men (Not much we can do about that).
-No matter how good you are, if you're a guitar player, you're looked on as "just another guy with a guitar". I've had the most success with banjo or Autoharp, even though I'm a much better guitar player. Now if I could just juggle chain saws I'd be rich.
-Keep track of the songs/tunes that make you money. These may not be your favourites, but...
-Know some kids songs. They often ask their parents for money to feed your case and they actually stop and listen.
-Smile and nod at people.
-I still have a big yellow sign in my Autoharp case that says in red letters,"BROKEN STRING FUND! Visa or Mastercard cheerfully accepted".
I've never had anyone try to use a credit card, but they laugh as they throw a buck in my case.