I agree, be available for your partner when they need you. Show that you love her and be sincere. Every once and awhile its a good idea to do something creative to spice up the relationship, this will help to increase the romantic energy between a couple.
One of the biggest factors has always been.... Be a good listener. Nothing will help you understand a woman more than being a good listener, and she will notice. When you show a girl that your a good listener, you show her that you sincerely care.
If you've been in a relationship for quite awhile and your trying to spice things up. Its a great idea to change things up a bit... Do something that isn't routine - even if it doesn't cost money.
Fishing, Hiking, riding bikes, picnics at the beach or at the park. Take the dogs for a walk and have nice talk... Make her a surprise dinner. Etc.