I'm so glad I don't make mix tapes anymore (like I used to in high school). Now that I have itunes, this is how my process works: After I realize I like a girl, I will first make a playlist folder for her. Then I will go through all the music I have added to my library in the past 2 years that might work and add that to a master list (usually 60-200 songs). Then I cull that list to about 50 songs over the next week or so. After that, I usually make between 5-6 playlists, each comprising 10-15 songs. I then transfer all the playlists to my ipod and listen to each one during my bike rides. Then I will settle on one or two. After that, I usually spend the next week organizing the playlist order at work [this is when my boss walks in and breaks my concentration]. About a week later, I give the girl the cd (assuming we're still dating).
I haven't done this in so long. And, now everyone knows about my OCDness.