Dress like a nice guy (we all know you're a dog, but the setting will make it better to look like a decent fellow)
Step2
Go to greeting card shop and wander around.
Step3
Develop a good reason why you are there. You'll need several stories depending on who you are standing next to and why they are there. For example, a hottie is standing in the grandma birthday section, you should probably have a grandpa birthday reason for being there. For example, "My grandfather is so great. What do you think of this card?" She'll already have noticed you anyway, so all you need to do is ask questions and act like you are listening to her story.
Step4
Migrate around to other sections. Try sympathy sections, dead cousins, pets, etc. Look sad. She'll be sad, too and you'll both have something to talk about. Of course, she'll be screaming you her story from her back in a few hours.
Step5
Invite her for coffee afterwards. There's always a Starbuck's nearby. And believe me, she's in no hurry. She's probably been there for 2 hours looking around.
Tips & Warnings
Smell great and be polite. It's not like picking up girls at a bar.
Girls go there for like 5 hours man. You'll have plenty of time.
Greeting card shops are the last place a guy would want to hang out, which makes them perfect. That is why when you go in, you're the only dude and you're surrounded by like 25 emotional girls.
No reason at all to go in the "For Her, For Him" section. She's buying a card for her boyfriend and she'll think you are scamming around on your girlfriend.
Stay away from girls with kids. That's a more general tip, not just for greeting card shops.
Valentine's Day. Why are you in there? Why are they? Be careful, but if you can find a single girl in there with no date, SCORE!