Grand Theft Auto IV

basically for the easiest way to do it is after you have met michelle and completed the mission, ring her and ask her to go out for a date and when she is free take her to the diner on 69th street and after your meal take her home and try your luck and she should invite you in if not on your next date do the same thing

It's certainly easiest to sleep with Michelle, but if you screw up and don't take her out before you lose the ability to date her (like I did), try Carmen Ortiz, the SoBoHoe. It takes 2 dates. You get her number on the first, and sleep with her on the second. Prep -
- Buy 2 suits from Perseus. If you're done with the story, you should at least have 1 from story missions. I used the obsidian and the charcoal.
- Get a nice car and park it at the South Bohan house. I used a Cavalcade.

Go to Tw@t and attempt to date Carmen on love-meet.net. 12-24 hours later, you'll get an email back. Go save a couple times at the nearest house to advance time, then wait around for a response. Receiving the email will put an appointment in your phone. Carmen's 1st date will always be at midnight, and her place in South Bohan will pop up on your map at 21:00-22:00. If necessary, go to the South Bohan house and save the game until the timing is right. Switch to one of the suits, grab the nice car, pick her up, and go to the strip club, which is close by. At the end of the night, she will give you her number. Wait a day or 2, call her, and repeat this same date with the other suit. She may complain and say something like "What is it with you and strippers?", but it doesn't matter. Try your luck at the end of the date, she will let you in. She also liked me enough to unlock her special ability--you call her and get a health boost.

I personally haven't verified this, but I've read that if you're going to play the Gay Tony DLC, you can also get the achievement via booty calls - http://gta.wikia.com/Booty_Call - This may be even easier than dating Carmen.

I got this one on the second date, I took her to the bar and she was all for it, I'm assuming the alcohol had something to do with it.

This achievement is harder if you wait till after you finish the story, but it us still possible. You need to find a computer (go to the nearest internet cafe), then go to www.love-meet.net , click 'female' under 'find love', then find SOBOHOE, click on her then press 'date'. Then, go to Perseus and buy both types of suit, and wear one out. Sleep at your safehouse on the middle island (with its own computer) until a few days later (repeatedly save so that time passes). Check the laptop in your appartment after every save for a new email. Eventually Carmen (real name of sobohoe) will reply to you saying that she wants to meet at 0:00 in a couple of days. So you need to wait a little longer then go pick her up around that time. Take her to a bar, go back to her house and ask for her number. Then drive to your safehouse and sleep until it is afternoon. Switch suits, then phone her and ask to meet. Take her to a bar again, then go back to her house. Press a to try your luck and the achievement should unlock!

The video below is a guide to all the dating in the game, I found it useful. The section on Carmen is part way through. Credit to 'GTA Series Videos'