Typically, to get completely free seeds, you have to be able to give something of value in return.

That means that they usually go to established experts in the field with a following who will promote the specific strain online or in print.

An alternative would be to keep a look out for free seed promotions. Most breeders and seed banks only give away free seeds when you buy other seeds, but you can find no-strings-attached promotions now & then.

A few months ago, we had several Twitter-based contests that gave away seeds for free. I don't think we have anything going on right now, but I usually post about them when they pop up.