seed planting

most of the time you will have a seed packet with instructions,
but sometimes you will not (like if you got seeds from food at a store you want to grow)
so here are some guidelines and thoughts that might help you,

if a seed drys out when germinating it will die.
so don't let it dry out,
this can be done with depth, or mulch, or watering often,
some seeds need light to germinate, others do not,
white paper can make great see through mulch if you need it,

if you have hard clay soil, then you should be planting shallower,
if you have light soil you can often plant deeper,

the typical depth should be about 4 times it's height (if it is flat on a table)

but beans and corn will usually come up much deeper,

some seeds, especially wild ones and many tree seeds need the cold of winter before they will come up,
so either plant when the seeds would normally be dropped to the ground and maybe wait a year,
or simulate the weather, and that is called stratifying
http://en.wikipedia.org/wiki/Stratification_(botany)

as far as spacing,
try to figure out how big the plant will be, and plant them that far apart.

I last did this with a silverline melon, (still growing)

got it at the store, and it was good,
so I saved the seeds and planted them this year,
I had no idea how big the plants got looking on the web, 
it turns out to be lots like a cucumber plant in size and growing habits (night pictures don't turn out so well)

now time to figure out what to do with my first winter squash of the season,
it is about the size of a lighter...

it likely did not get pollinated, and that is why it is so small, but not sure,
the plant was hardening off the stem to it, so I know it was done growing.