Bargaining should be done with goodwill so that neither party feels put upon. Use smiles and good humour. But beware: the business of bargaining can be brutal!
Adventurers will gauge their own comfort level of balanced, fair barter. A street seller starts at, let’s say, $20. I say ‘No, too much.’ (Often I don’t even want it!)
They say ‘OK, $15.’
I say, ‘It’s quite cute but it’s too much.’ (I still don’t want it.)
‘OK. How much you give?’
I say something stupid like ‘$5’.