I had this problem with a guy friend of mine after we stopped dating. I reminded him time and time again that I asked him to make an effort to keeping the friendship that he claimed to care about but he never seemed to make a change. Finally I started telling him how much of a loser it made me feel to always do everything (IMing first, doing all the calling, setting up all the hang-outs) and he seemed like he understood, but still didn't change.
Finally, after freaking out at him enough times about how he doesn't really care he started to act like it a little. So really, all you can do is try to mention it in different ways and be as clear and obvious as you can until he understands the words coming out of your mouth. Don't be crazy about it though, if he feels that you're just gonna whine at him about it he'll rebel and never listen to you. In the end, he may or may not respond the way you really want him to and you can't change that, but look out for little bits of effort to let you know if he's trying or not. That's all you can ask for.