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Not only will you look and smell more attractive, taking care of your grooming shows her that you're mature and capable of important daily tasks. Also pay attention to the style of clothes that she wears, and wear the same style of clothing, this will help her to relate with you and find you overall more attractive. And pay particular attention to these areas:   Shower at least once a day. Wash your hair, soap up all over, and rinse off. Use a nice smelling shower scrub as well, something not too feminine, but not too masculine either, maybe try a smell like mint, or lemon. Keep your mouth clean. Brush twice daily, floss, and use mouthwash. For help in the middle of the day, use breath mints and chewing gum. Manage facial hair by shaving daily. If you're growing facial hair, make sure it's trimmed to a uniform length, and not scraggly or unruly. If you tend to have a unibrow, consider plucking any stray hairs over your nose. Wear a combination deodorant-antiperspirant. Apply it as soon as you get out of the shower in the morning. Make sure it also doesn't smell too feminine or too masculine either. Wear clean clothes. If you find yourself scrambling for fresh laundry, consider setting up a regular washing schedule, like doing all your laundry every Sunday night. Being well-mannered doesn't mean you're boring — it means you know how to treat other people with respect, a quality most girls want in their boyfriends. Show her you know how to be considerate by doing these things for everyone, not just her:  Say "please," "thank you" and "you're welcome." As well as asking with a "I'd appreciate it if" or "I would like for you..." If someone is walking through a door behind you, hold it open for him or her. Avoid cursing or saying anything crude in public, or in mixed company. It's fine to relax a little around your friends, but try to show your best side around people you don't know well. For more help, see How to Have Good Manners. Everyone slips up and says stupid things, but try your best to limit it when you're around this girl. Take a few seconds to evaluate what you're going to say before you spit it out.  Don't talk up other girls. You might think making her jealous is a good idea, but steer clear. Discussing the looks of other girls in front of her will make you seem shallow and fickle. As far as she knows, she's the only one you're interested in. Avoid coming off as a bully. Don't throw out careless insults or put other people down, even if they're meant to be funny. She might not be able to pick up on your humorous tone and take your words at face value. Don't tell dirty jokes. There's a time and place for wicked humor — and it's when you're hanging out with your guy friends. Keep on a lid on it when you're around her. One thing you should say when you're around her is a nice, genuine compliment. It's not as difficult as it seems! Here's what to do:  Think of what you like best about her. It could be her smile, her laugh, her intelligence — whatever strikes you as her best quality. (The only caveat to this is that you should not compliment her on any physical traits except her eyes or her smile. She might have a great figure, but now's not the time.) Do it semi-privately. You don't have to get her completely alone to pay her a compliment, but try not to do it with all of her friends or your friends listening closely. You could also pull it off in a text or instant message. Keep it short and sweet. No need to wax poetic for three or four minutes on her best qualities. A simple one-liner will do. Pay attention to how you word it. Instead of saying "That's a pretty dress" or "I like your outfit," say "You look really great in that dress." Compliment the woman, not the article of clothing! Get the body language right. Smile! Keep eye contact while you say it, too. Find little ways to let her know that you think she's an extraordinary person, and she'll definitely notice.  Don't ignore her or play hard to get. If she texts you, text back. If she wants to talk, try to make the time even if it's slightly inconvenient. Go out of your way to help her. If she could use a hand with something, offer your assistance! It could be carrying heavy or cumbersome items, going with her to run an errand, or talking to her through a difficult situation. Let her talk. The #1 mistake when talking to a girl is focusing on yourself. Girls are way more comfortable when they talk about common interests. Ask about her interests, hobbies, favorite books, music, etc. If she asks you a question, answer it in a few, short sentences and then redirect the question back at her. This engages her in the conversation. Start an inside joke with her! By doing this the two of you will share a secret connection that is shared between only the two of you. This will make her feel special, included and closer to you. It will also give you an easy-to-come-up-with conversation starter. But keep in mind, if you overuse the inside joke, it could quickly go from fun to boring, so only use it when you must.
Dress to impress. Be polite. Think before you speak. Pay her a sincere compliment. Make her feel special.