harvesting seeds?

I have looked about and don't see much on harvesting seeds, logic (mine anyways) would say to let the plant finish it's life cycle completely and allow seedss to mature.

Anyone have some experience or knowledge to pass along it would be appreciated.

I have just tryed getting some seed for the first time. I found that you can atually see the seeds when they are ready if you look close. But from what i have been told just let the plant flower as normal and the seeds will be ready.

Here's something you can try:
In nature, seeds drop off the plant by themselves when ready. You can collect them on a piece of paper as shown. Make it sort of funnel-shaped so they don't bounce off.

Any seeds left when you cut it down you'll find in the buds anyway!:p

You can see if they are mature on the plant like LegalizeDaHurb says, they stick out with the familiar brown, and you can pinch them to check if they are hard. It takes 2-3 weeks for the seeds to mature. they fall right out when the bud is dried (a little help of course) I had two plants last grow go hermie very late in life, they produced some 60 seeds (between the two) and at least 20 from each plant are mature enough to germinate. Very glad my sativa dom seeded.