Summarize this article in one sentence.
Deep down, everyone is a nerd about something. Learn a little about her hobbies, or whatever makes her happy outside of your relationship. Show genuine interest in them, and she'll appreciate the effort. You don't have to fake enthusiasm, or even fully understand what she's talking about. Just make an effort to follow her explanations. Don't take the relationship for granted. Set aside time to give each other your full attention, and put in the effort to make it feel special. Does she stop to pet dogs on the street? Did she call something you did cute in conversation? Make a mental note of these moments, and she'll probably tell you everything you can do to make her smile without even knowing it. "Sexy" and "gorgeous" can be great in the right context, but people need recognition on other levels as well. Make sure your girlfriend knows you appreciate her intellect and skill. Every relationship is different. Remember to think of what your girlfriend enjoys, instead of repeating what worked on your last significant other. Sometimes, you have to let your girlfriend be mad, or sad, or whatever it is she's feeling. If she's going through a rough emotional time, don't tell her that everything's okay or that she just needs to cheer up. She should be able to trust you with every emotion she has, and seek support even when she's not up to smiling.
Discover your girlfriend's interests. Make time for her. Keep an eye out for what makes her smile. Compliment her on the things that matter to her. Wipe the slate clean from your last relationship. Know when to let her frown.