How do you tell a guy you like it?

Boys don't speak body language so you will probably disappointed if you try that. You could try something radically different, like saying mmm that feels so good when you massage my tits. You could open your shirt and take his hand and place it on your boob. That is what guys can understand, we are really not very bright about subtle hints.

If a guy was touching your breasts, and stopped, he probably thought you didn't like it, or he was doing it too much. Pretty much whisper to him, take his hand, put it on your breast, and tell him something, in like, a seductive voice, something similar to, "I like that" or "Oh, that feels good".

agreed with all the other responses so far

Just grab his hand back, then place it back on there. Easy as that.

You can react more when he does things you like, but I think the better way is to just tell him. You can do this in a sexy way, like saying "Oh keep doing that, oh please, you feel so good." Guys like it when we beg for something sexually. Really, he'll eat it up. They love any kind of reinforcement that we're as into it as they are.

I know for me and my boyfriend I sometimes put his hands on them. He understands :)