i'll ask, "do you anything on you that you're not supposed to have,,, do you mind if i check?" if they say "yes", i ask them, "anything that'll poke me, prick me, piss me off?" if they say "no" and i have pc to arrest, i'll arrest. i will normally find dope. if they say "no" and there is no pc to arrest, i smile and tell them, "next time!" one thing that's fairly universal about crooks. they'll still be crooks tomorrow....
i have conducted what we call, "knock and talk" several times and will always ask for permission to search. when i'm told, "no," i hand them a search warrant and insist! it's always easier to get consent, but if it's something you really want to search, get a warrant before you tip your hand!
vehicles are different. much easier to search.