There are a few ways to spice up your typical portrait:
**NOTE: All photographs used in this tutorial were shot and retouched by myself
Step 1: Personality
The best way to photograph inexperienced models is to just talk to them, and not nececssarily about the shoot. Talk to them about their favorite band, or sport, get them talking about themselves and they'll start to feel more comfortable, and their personality will come through more. Try to capture candid shots of them laughing or looking at a loved one to show how they really are.
Another way to loosten up and nervous model is to give them a prop to play with, or make the set easier to interact with. You can also ask them to bring a selection of clothes to wear and have a stylist put some outfits together, (or do it yourself if you've got some fashion skills.) The better they look and the more they enjoy the experience, the better the photograph will come out.
Again, shooting models can be difficult, just try to be friendly and relax and they will eventually get the hang of it.