During the robbery/auction, always make choices that are favorable to the girl. Agree with what she says, and choose to let her continue bidding without intervening.
After the car crash, take her with you to Mr. Woe's. After leaving there, go along with her plan and you'll arrive at the hotel. When she kisses you in the hotel room, choose to kiss her back.
Update: Per Cajeel in the comments below, here are more details to get this to work:
Be Altruist/help the guy at train station/Help the girl obtain the car without asking anything, Look the robber and goes to him, drive.
Don't let the robbers drug you, don't ask for reward.
Now, the important part:
At the auction,
-Be favorable with the girl when you goes out of the car
-Let her bid
-Take the elevator below
-Ask the security agent for the toilets
-Don't react when Leclercq tries to escape
-Enter the right code
Alarms won't be triggered to prevent next steps
If you did everything good, when you'll go out, you will enter the girl's car and have to clap in her hands.
Goes to Woe's, take the biscuit, don't negociate whit Woe, accept his answer.
Show the biscuit to the girl.
Follow her plan
At this moment, a cutscene showing the girl looking at you and you looking the girl in the cab must arrive. You know precisely at this moment that the kiss will trigger.