Well,a lot depends on what you want to grow from seed. Some such as hawthorn, whitebeam, i.e trees with berries, require stratification. That is the seed will not normally germinate until the hard seed coat has been softened by an outside influence. The natural way is for birds to eat the fruit, seed and all, the evacuate the seed onto our clean washing which, if it falls onto moist soil, may germinate.(the seed that is, not the washing)
Another way is the seed gets exposed to heavy frost which breaks the shell and lets water in.
We can do this ourselves by putting the seeds in the fridge for a few weeks or months,depending on the species, or putting them in a pot of sand and leaving the pot outside all winter. This takes longer of course but as the year wakes up (soon please!) the seeds break dormancy and grow!

Of course having posted the above you're probably wanting to grow seeds from Field maple (simple enough, just like regular seeds in a pot now) or pine which cant be grown from cutings by the layman. I've not had experience with pine seeds(well, Ive had one bad experience) but I'm sure theres plenty on here that have!

hope this small book helps,
Larry