Consider giving her a present for no reason. This is romantic and is even more special than giving her one when she expects it.
It's better to give no gift than to give one that screams, "I put no thought or effort into this!" For example, if it's her birthday and you're on your way home from work, don't just swing into the grocery store because it's on the way and buy a cheap bouquet of old carnations. Go to a florist and get a nice, big, fresh bouquet. Or order one ahead of time here.
You don't have to spend a fortune on gifts. If you can afford to buy her a diamond necklace or new car and you know she'd like such extravagance, go ahead. But don't substitute or equate spending lots of money with making her happy. What women love is a present that's thoughtful, appropriate, and timely. The expensive part is optional.
The sweetest gifts are those you make yourself. Even if you think you're not creative or handy with tools, there's probably something you could put together with your own hands. Bake some chocolate chip cookies. Buy a blank book and write how you feel about her. Make a CD full of love songs. A handmade present shows that you put time and effort into pleasing her.
Just a few random gift ideas for women: