There's lots of ways to do that. You could go in for a hug, but make sure you get real snug and close in his arms - body to body.
When you pull away, he will probably have a boner.
Another thing you can do is sit on his lap innocently. Maybe you get a little uncomfortable? You'll have to wiggle around a bit... ;)
Sometimes you don't have to even make physical contact. Like bending down to pick something up and accidentally showing off a bit more than intended. It's all good girl!