Maybe have a good stretch first...
You said you move your head, let your shoulders and hips pick up the same rhythmic sway your head is following...
Remember to laugh and smile, even if you're by yourself. It's supposed to be fun.
Do it for yourself, not for others.
Start with a mellow beat, once you've mastered that, you can move on to faster stuff.
There's a bunch of how to dance videos on youtube, but I honestly didn't feel like watching them to see if they're any good.