Blow Job Tips

So, I gave my first blow job to my boyfriend, but I know I wasn't very good at it. It sounds weird, but I had a hard time sucking. I did more licking. And my jaw started to hurt while doing it. He was laying down, so I don't know if that makes a difference. But I was wondering if anyone has some blow job tips? And how long did it take for you to get the hang of it?