Also depends on what kind of truck you have. I have an S-10 sportside, so my bed is kinda narrow. The straps were actually too long to just hook on the triple fork, so I had to loop them around the forks a few times. I'd also use 4 straps, like madav8tr said. Some people use two, but they're not paranoid like me.
When you do get it strapped in, you should be able to rock the whole truck by rocking the bike. basically they two should become one. /images/icons/smile.gif