The first question you need to ask yourself is whether he is too old for you to date. There is a rule of thumb on this: divide the older person's age by two and add seven. That will give you the minimum acceptable age for a dating partner. Thus, if he is 22, the math is (22/2)+7=18. (You'd, therefore, need to be 18.) This formula is only appropriate when both parties are over 18, of course. You don't specify your age. I personally think that 4 years is too much of an age gap until you get into your upper twenties.
If you're satisfied that age is not an issue, then make sure he sees you as a mature and confident young woman. Express your opinions, preferences, and personality without a question mark. Flirt with him and see whether he flirts back. Ask what he's looking for in a girl and engage in conversation about what you both want out of life. You can even ask whether he's ever thought of going out with you if you feel daring. You can also have fun with a game of "ask me anything."