Most grasses will germinate with one or two blades, but will quickly, during the first growing season, expand the number of blades.

You should sow more than one seed in each cell, or to each square inch of an open seed flat. Check the web for specific instructions on the number of seeds per cell for the varieties of grass you are sowing. Jelitto, linked below, is one source for such information. If I can't find appropriate information, I use the ultimate width of the grass blade as a guide. If it's a fine-bladed grass, I sow more seeds per cell, and if it's a wide-bladed grass, fewer seeds.

When I grow grass from seed, I transplant the small seedling clumps to nursery pots, usually 4" or 1 quart pots, to grow them on for at least the first season. Then they go into nursery beds for at least another growing season, before eventually being moved to display beds as almost mature plants.

What grasses are you sowing?

Here is a link that might be useful: Jelitto