First and foremost remember you don't have to have idealistic notions of what is considered romantic. Most people would prefer simple and consistent small gestures of affection more frequently rather than than a once or twice a year grand display.

Keep it simple, but let them know you are thinking of them. Write messages in the bathroom mirror for them. Leave post-it notes in unexpected places around the house or in their car. Put a funny picture of yourself in the book or magazine they are currently reading. Even something quick and simple will be much appreciated and remembered because it showed you thought about them.

Be careful not to do something that may make them feel uncomfortable. Public displays of affection, embarrassing them at work, etc make some people uneasy. Remember to keep it within their comfort zone.

Asking them simple questions and listen to the answers. Pay attention and try to show you heard what they said.

Make a special date night just for the two of you. What you do is really not important just as long as it is something you both enjoy.