Supposedly there is something in the semen that can help the cervix progress. It is a little like the castor oil thing - you might go into labor, and you might just have some sex. Either way, it doesn't hurt anything (unless you've broken your waters. You do not want to have sex or insert anything into the vagina if your waters have broken).
The pressure is what you want when you walk. You cannot take a passive role in birth. You will be forced into an active role. Try this: stand facing your partner. Wrap your arms around his shoulders and have him wrap his arm around your waist. Keep your feet hip distance apart, even a little more than that. Sway your hips in a circle. Let him take most of your weight, if you can. Keep moving your hips in wide circular movements. This will encourage the baby to move down the pelvis.
You can sit on an exercise ball and move your hips in the same wide circle. The gravity of these movements help the baby come down.
When is your due date? Are you post dates? Your doctor or midwife probably has some other natural induction methods you might wish to try.