Be well-groomed. This is essential if you are even going to approach an attractive girl. Brush your hair, shower, wash your face, brush your teeth, use deodorant and maybe even a little cologne, and apply acne medicine daily (if you have a problem with your skin). Don't wear your pants off your butt, often called "sagging": it's not that attractive to the majority of girls. Wear clean, attractive clothes that fit. (If in doubt, get an older sister or close female friend to help you in this department.) Don't wear skin tight clothes, but don't wear clothes that are too baggy either. Girls hate that.
Have a great attitude. Be fun to hang around with, easy to laugh with, and be outgoing. Just don't be full of yourself. A girl may like an overly cocky guy at first, but eventually, she will find it selfish. Don't try to impress everyone: girls like humble guys. At the same time, a sense of humor is always good. Girls love when guys can make them laugh.
Show respect. If you respect everyone and give them their space, they'll all respect you. With girls, it works even better. If they see you respecting everyone, and not getting pushed around while you're at it, they will be reassured that you will treat them right. Be kind to all.
Have nice conversations. Try to aim for you both to be speaking half of the time, but make sure that you are saying something worthwhile. It's not attractive when only one person talks endlessly or when they say bad words. Another thing to watch for is her attention. If she isn't paying complete attention, do not repeat yourself several times. This makes girls feel you are desperate, and usually annoying.
Show interest in her. 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 their 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. When in doubt, compliment her like your hair looks nice today. Even if a girl does not like you yet, complimenting her will make her feel good about herself and think positively about you. However, if she keeps redirecting the conversation back to you, talk about yourself, otherwise it seems like you don't really want to be talking to her.
Try flirting! Don't be obsessive! If you both make eye contact, do not be the one to look away, but do not stare for too long. When you both make eye contact, just give a slight smile. Touch her arm or shoulder for a few seconds. Physical contact is a great way to show you're interested. If she seems uncomfortable, do not do it again.
She may look away and she might blush a little. Be careful though; you don't want to stare her down. A good move is to look away, and if she likes you she will shoot you glances. Watch for that. And be courteous. Open doors. Do kind things, girls love that.
Respect her friends and their ideas and opinions. Always speak highly of her and never talk trash about her. It will damage her reputation and yours. Hopefully then it will work both ways - she will be tolerant of your friends. Be careful not to compliment her friends too much, however. Example: You may say "Your friends seem cool. We should hang out with them and my friends some time, I think they'd get along". You may not say "Sally is so hot. She has the nicest eyes". You may think getting her jealous is a good idea, but it just makes them angry.
Have your friends be nice to her It's a fantastic thing when your friends don't make a total fool of you. Warn them ahead of time and avoid topics pertaining to embarrassing moments of your past or awkward jokes that make very little sense. Don't introduce her to your friends right away though. You want her to like you, not start dating one of your buddies. If your friends like to embarrass you, try to avoid them altogether.
Be polite to her parents. Be kind to everyone, especially them. Don't be too over-the-top charming with the parents, however, or they'll think that you have something to hide.Be willing make sure that you and her father get along as he will be looking out for his daughter.
Don't criticize her. Unless she asks for constructive criticism. And even then she probably wants you to compliment her.
Be romantic. but not over the top. If you've been dating for a while you may attempt a grand romantic gesture, otherwise, you'll look like a stalker. It's also okay to be a little cheesy, like giving her a bouquet of roses and a loving poem. It may sound like a bad idea, but girls will find it thoughtful if it came from your heart. A better idea than being cheesy is to really LISTEN to her and remember things she likes. Then take her somewhere she's mentioned wanting to go, or buy her the books she's been wanting and hide a little note inside. Flowers and candy are really cliche and don't really mean much since anyone can just buy someone flowers. Showing you've been listening to her wants and needs goes a LOT farther than roses!!
Start talking to her casually. If you don't know her, make friendly conversation. Ask for the time, and/or compliment her watch. Avoid throwing too many compliments about clothes or shoes around: that might make women think that you are homosexual as many gay men are fashion-forward.
Do not play "hard to get". Sure, you'll get their attention for a day or two then after a while, the girl will end up frustrated, and she'll think you don't find interest in her anymore.
Be careful with what you say. Do not discuss bodily functions in her presence, or make jokes of a sexual nature unless she starts doing so. Also, don't discuss anything gross or inappropriate. She'll get grossed out.
Hum in her presence. She might think of you whenever she hears that song. And she'll probably be impressed by your good taste in music. Some girls have actually dumped guys or stopped liking guys when they insulted the music they like. So, it's OK not to like her music, but don't be insulting her favorite singer(s) or band(s)! Try to figure out what music you BOTH like.
Start an inside joke with her! She will feel included and become closer to you. It also gives you an easy-to-come-up-with conversation starter. Try not to overuse it and kill the joke.
End later meetings with a hug, or plans to meet some other time, if you can. Make sure to tell her that you enjoyed her company.
Tell her that you "like her" frequently. Ask her out.
Touch her occasionally, like on the shoulder or hand. Be sure do not touch her private parts, however.
Opposites attract. Be a courageous gentleman, not coy like a lady might be.
Show your funny side. A lot of women look for sense of humor in a partner. You should however be mindful of their reactions to your jokes and avoid offensive humor. Unless they like that. Find out if she likes comedy. If she watches Comedy Central or other readily-accessible comedy, find out her favorite comedian or favorite impression and try something along the same lines for her.
Make her feel good. This is a really good thing that impresses girls. They love it when you let them know you care for them. If she's sad, just simply put your arm around her neck. Make her happy as much as you can. Flirt with her, hold her hand it will make her feel special.
Don't ever make fun of your friends around her. If you do, it might make her think that you're a jerk. When someone makes fun of other people, it makes a woman wonder what they might be saying about HER when she's not around!
Be honest. Do something creative, something extraordinary or something that others never do. That creates a question mark for the girl about you, and it also makes you interesting.
Be open. Don't share too many secrets with her. Sprinkle a little and don't irritate her asking repeated questions. Always keep your face glowing and charming.
Don't ignore her. Don't ever ignore her messages such as through phone calls, text messages or Facebook. Make her feel like you always have time for her.
Tease her. Believe it or not, most girls liked to be teased. It can be about something she said or whatever. Just make sure you don't overdo it and always use humor, you don't want to come off as a jerk.