How to Make Your Girlfriend Happy?

Show her affection.

Girls want guys to show them affection because it tells her that you care about her, and that you're willing to show that love in a public way. It doesn't always have to be public (PDA), but get used to the idea, because she wants other people to see how much you love her, so don't be afraid to kiss her or hold her hand in public.
Tell her she's beautiful and always make eye contact. Eye contact shows you mean what you say. When you look away, it will make her question your authenticity, so make eye contact at all times. You have to show her that you mean what you said. If you're really sincere when you tell her how beautiful she is to you, you're going to go a long way.
Also, tell her that she drives you crazy, and that she's the prettiest girl you've ever laid eyes on. Tell her that you've never met anyone like her.
Compliment her on her looks, but also on her accomplishments, talents and abilities. If she's a great poker player, tell her she's smart. If she's a good listener, tell her she's great with other people.

Listen To Her

It's become a familiar cliche: Men don't listen, and there's not much that can be done about it. For 2018, why not give up the lazy stereotypes by practicing active listening. It's not particularly difficult: You ask her how she is or whether everything's OK, and then sit there with open ears while she answers you. Resist the impulse to try to immediately fix everything: Sometimes she just wants to be heard, and the simple act of listening and reassuring her that you care is enough.

Tell her you love her.

Make sure you mean it. If you're not ready to go there yet, that's fine. But, be sure to switch that "I love you" for a really good "You know how special you are to me?" or a "I like you so much; I'm a really lucky guy."
Simple is best. Stick with "I love you," or "You make me so happy," or "I'm really lucky to have you." Don't be so poetic that you go overboard.
These statements make her feel good, and they make her self-confidence soar. Remember, when her self-confidence is high, you benefit. Be steady with your signs of love or affection, enough so that she doesn't forget how much you mean to her, but not so much that the power of the words gets watered down.

Buy Her Thoughtful Gifts
If you trot out a variation on the same theme year after year, or worse, have resorted to getting your girlfriend gift certificates every birthday and Christmas, it might be time to pull your socks up in the gift department. In the weeks leading up to the event, pay attention to clues she may be giving you about things she’d love to receive, or try soliciting help from her friends, who might be able to offer a fresh perspective. Also, checking her Pinterest or Amazon Wishlist will almost certainly help you find a tailored and appreciated gift.

Show An Interest In Her Interests

If your girlfriend has a hobby or passion that you've always effectively ignored, boost her esteem by showing some interest in it. You don't necessarily have to take part yourself, but showing up to watch some of her soccer games or providing positive feedback about her blog will make her feel valued. Mutual respect is the glue of successful relationships, so if you've been acting as though her interests are trivial or incidental, it's time to start showing them some enthusiasm.