It's easy to manipulate people you know well. My best friend doesn't always want to go out and do things, but he heeds the beck and call of his girlfriend. So basically all I have to do is convince her to do something, then it becomes two vs. one and very easy to to get him to cave in. Do it all the time.
On the flipside, it may just be my ego talking but I don't think I'm very easy at all to manipulate. I like to think my bullshit detector is finely tuned and it isn't hard for me to put the brakes on anything that is getting pitched to me. I've been told multiple times that I'm hard to figure out, I just love to keep people guessing