First, I chose two of my very favorite "love" quotes:
"To love another person is to see the face of God." - Victor Hugo, Les Miserables
"It was a million tiny little things that, when you added them all up, they meant we were supposed to be together . . . and I knew it."
- Tom Hanks in Sleepless in Seattle
Then I just took a deep breath and started writing with my Sharpie.
*Tip: If you mess up big time, use rubbing alcohol (or nail polish remover) on a cotton ball to take off the Sharpie and start over again. This was my saving grace on the second mug.
That's it! Enjoy your $1 mugs with your sweetheart.
Post edit: I changed the oven time from 30 minutes to 2 hours after reading plenty of other people online whose Sharpie wore off after a couple washes in the dishwasher. In mugs I've made in the past with this method, the Sharpie hasn't worn off. I'll keep you posted about these. :)