Apart from choosing the repertoire for the moment
if you amplify don't make it so loud the poeple can't be bothered to get near enough to give.
& one Dave Hart in NZ used to reckon was to pick rhythms that match the passers' by footfalls and lift ther spirits. Mind you he only played on a Fri mornoing in a subway from the train to bus station. Last working day of the week people want to be happy he magnified that a bit. Dance tune and shanties were his choice - rhytmical.