Know your cycle
Most medics agree that women are more likely to get pregnant within a day or so of ovulating.
You normally ovulate two weeks after the first day of your period, so having lots of sex at this time of the month is ideal. While sperm lives for up to 7 days, eggs have a much shorter lifespan - they only 'live' for 12 to 24 hours once they have been released so you might want to schedule special baby making appointments with your partner when you know you're at your most fertile.
But that shouldn't stop you from going for it at other times during your cycle, as we've said, the more the better!
Check out sofeminine's Ovulation Calendar Tool.