I'm dipping into my bag of tricks here, but let me give you an idea. If you have been with her for awhile you've probabily done some traveling with her. There is probabily one specific event that you both really connected on and remains a great lasting memory in both of your minds.
Take her to dinner with a group of friends. Start a conversation about the special times you guys had together at the destination. Embarass her a little bit, seriously, talk about a romantic time there and make her blush.
Then pull out tickets for THAT weekend to go back to the same place. The women at the table will will give the "awwww, that is so sweet" thing and your position will be elevated. With all the conviction in your soul, just look her dead in the eyes and tell her you love her more today then you ever imagined you could back then.
When the evening is over, you will be rewarded. Spend the extra 8 minutes and snuggle the crap out of her.
TRUST ME.