Different ways to give oral sex?

My boyfriend and I have been going out for about two years now. I've given him head plenty of times, but sometimes when I'm really not in the mood, I rush through it, stop before he cums, or just gag a lot and stop. Recently, he asked me to try something a little different when I do it. I know that I tend to do the same thing every time, but I'm just a little nervous about how he'll react or if it's even going to feel good. Basically, I'm just looking for some different techniques or good ways to give h ead. I just want to spice things up and make him happy. Any advice?