So when is the right time to have sex? Too soon and you're seen as being 'easy'; leave it too long and you're either seen as frigid or you risk losing your date to another more willing partner because they assume you don't find them attractive.
Nevertheless, you should only have sex when it feels right for you - when your instinct guides you in that direction and you feel happy, relaxed and comfortable.
However, if you're looking for something more than just casual sex, then it isn't such a great idea to jump into bed until after the first few dates. It's worth holding out for a while, especially if you think your date could have what it takes for a serious relationship to develop.
Sex is more or less freely available to both men and women - go to any bar or club, and if it's what you're really looking for, you'll probably find it. So if you hold off from having sex right away, you'll immediately make it more special. A guy's basic instinct may be to try to get you into bed, but if he thinks that you might be relationship material, then there'll also be a part of him that wants you to say 'no'.
However, if he's only looking for a one night stand or a quick fling, a refusal will probably make him give up and move on to the next person. This may hurt at first, but remember, if that's the way he was inclined he would have moved on anyway, so at least you've managed to come out of the situation with your dignity intact.
The reality is that we need to know a little more about someone before sex feels right. Even if we're not expecting it to lead to a long term relationship, we need to know if we're compatible and whether we think we can make each other feel good. If there's real chemistry there, it will only intensify the more that you get to know each other.
Of course, there are always exceptions to the rule. I'm sure that there are people who jumped into bed together on their first date and are now happily in love 20 years later. However, do bear in mind that whilst there aren't many people who regret not sleeping with someone earlier than they did, there are plenty who wish that they'd waited longer ...