If that cute girl in Spanish class has caught your eye, you might want to give her a compliment to show her that you are interested. The right type of compliment is genuine, considerate, not given too often and offered without the expectation of receiving anything in return, according to Susan Krauss Whitbourne, a psychology professor at the University of Massachusetts Amherst. Offer a compliment that has all of these attributes to make the best impact.

Compliment Her Personality

In a study published in the journal "Women and Language" in fall 2006, over 90 percent of compliments offered by male college students were about a girl's looks or skills. If you really want to give a compliment that stands out to your crush, consider saying something about her personality. Tell her she has a quirky sense of humor that never fails to make you laugh, a friendly charm or a caring nature. She probably doesn't hear those types of compliments often -- and she will be left thinking about you longer.

Be Indirect

If you want to offer a compliment without being too direct -- consider phrasing your praise in a way that your crush flatters herself. Jack Schafer, Ph.D., professor of law enforcement and justice administration at Western Illinois University, offers examples such as, "How do you manage to stay in shape with your busy schedule?" or "I haven't met one person who didn't like your home-cooked pies." Your crush might reply by saying, "I work out five days a week" or "Yes, I have received lots of compliments on my pies" -- and in doing so has acknowledged that she indeed is in good shape or makes great pies. The idea is to phrase your compliment in an indirect manner, so that your flattery comes across as subtle.

Don't Be Desperate

Giving too many compliments can make you seem desperate, says dating coach Rebecca Dakin -- whether you are or not. In contrast, if you give compliments sparingly, you will seem like a strong and confident guy who knows what he wants. Only give compliments that are honest and sincere rather than doling out praise indiscriminately. The goal is to let her know that you like her -- but not overwhelm her or make her feel uncomfortable.

Don't Be Creepy

When you have a crush on someone it can feel like you know that person intimately -- and there is a risk of getting too personal with your compliments. For example, don't say "I love the smell of your hair," while leaning over and taking a whiff -- unless you know her really well. Remember that the object of your crush might not feel the same way as you -- and if you come on too strong she may think you are being creepy. If she does like you, being respectful of her boundaries and personal space will make her feel comfortable to eventually get closer to you.