First of all there are a number of things a man may be thinking after he sleeps with a woman on the first date.
The first involves his ego. He will think you really, really like him and his ego will skyrocket. Beware; he may sing in the shower. He will think he is the man and that he's just scored a friend with benefits. On the other hand, he may wonder whether or not you routinely sleep with every man who buys you dinner and be slightly repulsed. An open contradiction isn't it?
If the horizontal mambo continued late into the night and you fell asleep, don't start making excuses for your behavior the moment you wake up.
In this situation, many women will turn to the man and sheepishly explain that this is the first time they've done this. "I don't usually do this but it seemed like we had a real connection. . . " etc. Save it. He's probably heard that before and it is the precisely what he expects to hear.
Do not start talking about commitment.
Don't even commit to a second date. Graciously get out of bed, put your clothes on and explain that you have a busy day ahead and must get going. If by some chance he offers you coffee and breakfast do stay a little longer, however don't linger and don't go for round two. If you find yourself having breakfast together the morning after, don't discuss the night before. Again, don't explain yourself to him or make excuses for having slept with him on the first date. Talk about anything else; think along the lines of current events and other neutral topics.
Before you leave give him a peck on the lips and tell him you had a wonderful time.
Then go home. You may be tempted to send him an email or a text message later, again, explaining yourself or stroking his ego but this is one urge you should resist. Here is why; you want to exude confidence not insecurity. If he is a man of substance he will not judge you negatively just because you slept with him (especially if the date went very well, and the sex was great) he will however judge you on your post-coital behavior. Wait for him to contact you.
When he does contact you and he will even if only for sex pay close attention to what he says.
If he asks you for a second date don't accept if the second date is to take place at your house or his. Don't say something along these lines "Well, I don't want what happened last time to happen again, I'd like to get to know you better. " Politely decline the offer and go on about your business. If he really wants to see you again he will realize his mistake and try again. Accept only if he invites you to do something non-sexual together and don't end up in bed again. Tell him that you have an early meeting the next day and must prepare, or a class or whatever, just don't end the date between the sheets. Do kiss him thought. Suddenly becoming totally oblivious to his physical advances will tip him off to your insecurities so let him cop a little feel again, but leave him wanting more.
Avoid all this trouble by not sleeping with any man on the first date.
Unless you have no interest in him personally and are only looking for a casual fling. Nothing wrong with that; women need physical intimacy too. Do however use protection and enjoy yourself.