There are a number of things that you can do to increase your chances of conception.

Best Positions
The man-on-top position works well when trying to conceive. Place a small pillow under your hips following intercourse so that your cervix basically rests in the pool of semen for a short time (perhaps 20 minutes or so). This will allow the sperm time to easily swim up through the cervix. (Important Note: Do not use a large pillow, or you may sabotage your efforts, since the sperm may then puddle behind your cervix. Not a good place to be when trying to reach that egg.)

If you have a tipped uterus, you may have better luck having intercourse from behind (hands and knees position). By having intercourse in this position it allows the sperm better access to the cervix.

Positons to Avoid
For most women it makes sense to avoid straddling their partner while making love -- woman-on-top, sitting or standing -- since this can cause the semen to leak and may result in fewer sperm making their way to the egg.