There are several patterns on Ravelry that will help give you an idea of size and maybe pattern for a lap throw. There's quite a variety of sizes (from 27x38" to 48x48" with lots of sizes in betwen) so it will be a matter of your preference. The number of stitches to cast on will depend on the yarn and needle size that you're using and also the pattern stitch.
its just a basket weave pattern ,but not too difficult
wow that actually sounds pretty
I dream of a world where there is kindness, not hate. Even loners yarn
✿•*¨`*•. (¯`v´¯) (¯`v´¯) .•*¨`*•✿
. . . ✿•*¨`*•.¸(¯`v´¯)¸.•´*¨`*•✿ . . .
I like basket weave patterns, they're pretty. I think the size 8 needles might be a bit large for the DK yarn. Try a swatch and see what you think. You'll need to swatch to get your gauge and determine how wide 78 stitches will be.
Happiness is catching that dropped stitch while it's still fixable..