Bun venit Ionel.
If these are native plants you are thinking about, it
should be fairly easy.
Wild flowers generally set/drop seeds at the end of the growing season.
These seeds then overwinter, and germinate in the spring.
So, if you are collecting them, and taking them home to save for next spring, you should try to imitate your
local winter.
This usually means putting them in the refrigerator for a few months prior to planting.
As far as planting depth, a good general rule is to plant them 2x - 3x their size...a 10mm seed would be planted 20-30mm deep.
Scarification could be a little trickier, as some seeds do need to be passed through a bird, or other wildlife in order to help break down the hard coating. If in doubt, try soaking them in warm
water overnight before planting.
If it is trees/shrubs you are trying to grow, may I suggest this site:
http://www.treeshrubseeds.com/catalog.asp
They have one of the most diverse selections of anybody in the U.S. If you click on any species, a smaller window will open, and it gives good information on whether the seed needs special treatment (scarification or 'cold' treatment. etc.). They also show minimum/maximum hardiness zones that the
trees do well in. The site gives good info on thousands of varieties.
Noroc, John