use the mature fruit and make sure you use latex gloves when seeding. just slit it open and remove the seeds with a paring knife. be sure not to leave any of the pulp on the seeds as this could ruin some of the seeds. I generally do this on a paper plate or sheet of heavy paper then dump them into a dixie cup and set on the fridge or by the window to dry. (be sure to stir them daily to make sure they all get the air to dry out) after about a week or so I then place them into (depending on the amount of seeds) film containers, or small envelopes (get em at staples No.1 coin envelopes). If you plan on doing alot of harvesting of seeds and trading you might want to get the film containers. they hold an enormous amount of seeds and are free. just go to any one hour photo shop and ask them if they have any of the film containers for a project your are doing. they will most likely give you a big box of them. I picked up about 200 of them today from the local cvs. they work well and you can label them with masking tape or permenant marker on the lids. if you can try and get the black ones but any will work just fine. good luck with the harvest this year!
Sean