This counts as a failed date, even if you're on the way home from an otherwise successful date. If it does, date her immediately until it is above 0%.
A higher minimum is adviseable, but at the very least keep it above 0%. If you let a girl's respect for you reach 0%, and then date another girl, your current date will always once be caught by a jealous date whose respect for you is 0%.
There are two answers to this situation, one better than the other, but both bad. If you go too near the jealous date, both parties have caught you cheating. If you go far enough away from the jealous date, only the jealous date has caught you cheating, and the current date can still be a success.
This remains a bad situation however, because whoever catches you cheating will dump you the next time you see her, no matter what else happens.
To start a date with a girl, simply go to her house.