The organisation I am placed with runs a youth football league on Saturdays. I turned up in week two to take photographs for their newsletter and have not missed one since.
I am a poor footballer and that has been an advantage. Being visibly bad at something in front of people is a fast way past the stage where everyone is polite with you.
What I actually do there
Mostly logistics: bibs, water, keeping the under-tens from reorganising the fixtures themselves. Occasionally I referee, which nobody respects and everybody argues with, exactly as it should be.
Three months of structured fieldwork taught me less about this neighbourhood than six Saturdays of being shouted at over a throw-in.