Women may seem so complicated but I realized that everything that women want may boil to these things: communication, emotional assurance, and physical intimacy.
Let me elaborate further.
Communication - If you make everything clear to her, rest assured you won't get into trouble. She will not have doubts or suspicions on you. So tips to guys? Be open to your lady, tell her everything even the tiniest detail (whereabouts, plans, etc.), and never hide anything.
Emotional Assurance - Women are emotionally driven creatures thus as a man, you must do things that make her tick. Get in touch with her emotions. How? Treat her well. If you treat her well, she'll feel that she's being loved, cared about, cherished, treasured, and she will trust you as well. Honestly, I find it weird for some men ask "how could I show my love for her?". The answer is there, treat her well. Be thoughtful, spend time with her, be creative, be a gentlemen. In short, get in touch with her emotional side.
Physical intimacy - Physical intimacy includes but isn't limited to s3x. Kiss your lady, hug her, cuddle her. These little things mean a lot to her. But of course before doing such things, win her emotions first. Going a little bit higher, s3x is very important in relationships. But of course know your limitations.