It's all about confidence! Maintain the attitude that she is lucky that you like her (make sure you are smiling, and in a nice way)--and if she doesn't see that she is lucky--well, there are plenty of girls who will. If you are not that confident, or you are shy, you should work on this dilemma by trying the ideas with some girls who are not your special crush. Learn the process with some nice girls who are friendly, and are not too scary.
Work up to that special one when you have had some good results with this process (and feel like it). Having butterflies in your tummy, and a catch or shake in your voice is fine; just don't give up or fall back just because it makes you feel shaky: that is actually a sign that she is impressive to you--tell her that she impresses you if you want to. Be prepared to tell "what and why" you notice her (to show that you mean it)...
Compliment her: Tell her she has a beautiful smile or beautiful eyes, but do not say something that is not true. And--don't say them one after the other! (It is highly recommended that you must talk about other things before complimenting or else it feels awkward)
Girls like it when boys try to defend them when someone makes fun of them or threatens them. However, in other settings like a workplace or college, these things would rarely occur.
In most cases, if you pick on her and pretend you hate her, then she will never like you. She'll think that you do not like her, so she won't like you.
Girls feel at home when you talk to them honestly and openly, so try doing that.
NEVER say to a girl that she is hot, it might make her very uncomfortable--like an object; say she is pretty or beautiful instead.
Give her your phone number, MySpace, IM, etc. when you know each other well enough.
If she asks if she looks bad or stupid, say no, NO MATTER WHAT YOU THINK. Never pause and think though that makes her think your lying
Don't talk about just boy stuff like the details about football or something else in which she's show no interest. But don't talk about really girlie stuff either or else she'll think you're gay. Try finding a neutral zone to talk about what kinds and why she likes movies, cars, foods, animals--see which ones of those she likes, ask "how" or "why not," etc.--and school, her friends (mostly) or straight music (not really weird stuff) or anything like that. Just let her set the pace and get her started and you listen closely. Listen twice as much as you talk. Show an interest in her interests--ask questions--like "who or what", when and where, "how or why"--but don't interrogate her like a spy--or like it is a fill-in-the-blank test. Be casual about it. Let it work, let if sorta flow naturally... from one thing to another. Ask about things that you like, but not to just argue! Don't be too picky (hard to get along with) or too silly (and don't grin too much...). Be more natural... relax a little, but lean toward her a little bit, and be open to her ideas, to show interest.
Tips
A note about affection: it's good to start small, a touch on her lower spine will make her warm towards you, and quietly going up behind her to cuddle is less freaky than the full on front hug, and she can easily walk away if shes uncomfortable. You can also (if you are some what friends and the kinda person who would be kind like this) say you want a hug sarcastically and most girls (this is coming from a girl) will giggle and hug you. :)
Remember this: Do not just come out and openly say that you like her because that would put her in an awkward position and the results might not be what you want them to be. Ask her, "What color are my eyes in a soft nice voice." To maintain eye contact look one eye and then the other (repeatedly) instead of staring.
Give her a real compliment and tell her why--not a list--girls don't like too many compliments; it starts to freak them out. A guy will become the total opposite of a crush if he is too much of a fake and seems as if he is just doing a "job" on them. Be slow, cool and calm about it. Laid back--but not like you don't mean it.
Say "Hi" in the hallway, if you happen to walk by her. This will tell you whether or not she wants to say hi by her facial expression.
If she looks like she would say hi back, then go for it. But if she doesn't, try another time.
Be friendly, but do not crowd her.
When you smile at a girl it makes her feel great.
After making friendly conversation with her, try holding her hand or maybe hugging her. You don't want to go too fast, though. Make sure you only go as far as she wants to.
If you want to Be a Good Boyfriend then help out with things, bags for example and things that she may find heavy.
most girls have very good connections and news spreads around very fast, if you are at all mean or disrespectful, you will be in the bad books for a while.
Things that girls love
To talk: let her tell you stories. When she does DON'T TRY TO BEAT IT. If you have a similar story share it, but do not get competitive.
To be important: make things about her, and keep talking about what SHE WANTS.
To be protected: But be careful with this, because IT IS NOT YOUR JOB. Don't go overboard and act as if she is yours, she is a person and wishes to be treated like one, not like meat. Let her know that you care without calling in the Secret Service. Be careful, more independent girls might resent this.
If you get scared take a deep breath and remember why you are doing this.
Make sure you don't look too shabby or she'll think you're a loser.
If you don't think she'll like you, still try because just talking to her after a while might make her change her mind about you.
Always give her a stare--not at her body; that's a creepy stare--but stare at her face and eyes to make her think you like her, and when she thinks you like her then she may start having feelings for you.
Warnings
If the girl doesn't like you and SHE says it, don't keep pressuring her, you'll look like a stalker. If she tells you, don't say "It's your loss."
Also remember that EVERY girl is different - therefore, there is no specific set of steps to magically get your object of affection to like you. The reason she likes you is because she likes you for who you are. So just be yourself; no one likes a poser.
When giving a girl compliments, make sure not to over-do it. If you've just told her that her eyes are beautiful, don't immediately compliment her smile.
IMPORTANT-Don't compliment her unless you are sincere; tell why you think that in a realistic way. She'll see right through you if it is not explained. Point out something that makes her special and unique--and why...
It will be difficult to maintain this with a girl who has a boyfriend.
Don't look at her breasts (one quick glance is okay)! She might feel sexually harassed, or she'll think that that's the only thing you like her for.
Remember, not to look at her body all the time but just her face,she might think that your only sexually attracted to her. Looking at her maybe with a smile makes her feel good from the inside, and can make you come to her.
One big thing about compliments. Try and compliment something that you know she worked hard on, not something like "I like your eyes". Compliment her ensemble, how she did her hair, or how radiant she looks that night.***
Remember don't always talk about yourself, girls like to talk about their day... for a horrendously long amount of time.
Girls are not sex objects! Keep it clear that each girl is a person and has a mind to deal with in a reasoning manner! Find some common interests, and share ideas.