well one way to let them know what feels extra good and to stay in that spot is to come out and say "that feels good"
if you are like me and too shy to just come out and say that...
other hints work.
like if im b/f hits a certain spot or is doing a good combo of things ill either let out a sigh or moan to inform him he hit a good spot
if you dont give them some sort of reaction whether its good or not they'll just figure that's not the right spot so they'll move on and try other stuff. if he hits a GREAT spot and you are getting close just say "dont stop" or "that's it..keep going"
men can't read our minds...lol and sometimes not our hints either.