how do I vacuum seal food and seeds?

Vacuum sealing products these days have gotten pretty dang cheap.
Unless you do this type of work everyday and all day, a small, conventional vacuum sealer from amazon or ebay should suffice.

The only reason I recommend using the method of purchasing a product is because I think it would cost more on your part to make one.

Of course, you can just get the air tight zip lock bags, grab your vacuum cleaner... and just suck the air out and try to close it before air gets in? lol

Hope it helped!

. The mini-vacs that are used to clean computer keyboards should work well to clean the seal food, but you need to talk to a marine veterinarian about trying to vacuum seal seed.
.  Other than that, the others seem to be on the right track.

Have you seen this one? Looks like a good compromise between DIY and commercial solutions.

The easiest solution is to use a commercial vacuum sealer - the process is the same diy but a bit more complex.

Extract air from bag, seal bag with hot bar.

You can do it with different methods like jars.  A mason jar, with a small hole poked in the lid, and a piece of rubber taped over the hole can act as a one way valve.  Use a plunger-esque attachment to suck the air out, and the rubber will seal against the hole, keeping the vacuum.