So as a new homeowner I'm new to the whole lawn thing. I want to spiffy up my yard a bit planting grass seed (not sure what type yet), but I'm unsure as to when to start looking.
In general, what is the best time of year to plant grass seed?
Spring and fall are excellent times to over seed with new grass seed. You can improve the success by top dressing with 1/4" to 1/2" of compost or good weed free soil.
That being said, timing is everything. Sow seed too soon and it will not germinate until soil temperatures reach 40 to 45°F and day length is long enough. Wait too long and the seedlings could find it hard to establish if you get an early summer.
In the fall you want to allow sufficient time for the grass seed to germinate and establish before frost. Where I live that is September, no later than October but your area may be different.
Over seeding and top dressing twice a year are a smart gardener's best methods to improve the appearance of your lawn, reduce weeds and reduce the need for fertilizers with minimal cost and time.
My father in law always said the best time was to scatter the seed on the first snow in the fall. You could see how much you were using and how even it was. Then in the spring when the snow melts, there will be water for the seed. I think that matches pretty well to how wild grass propagates: the seed forms in the fall, eventually falls or blows off the stalk (or animals/birds help the process) and reaches the ground sometime in the winter, then in the spring it "wakes up" at the appropriate temperature and assuming it is on soil and there's water, it grows.
If you won't hurt your lawn by walking on it (around here the ground can be very soggy in the early spring and it's easy to compact it, or to pull grass out with your footsteps) then go ahead and scatter some seed on your existing lawn. If you have no existing lawn that's a different story, because you might need to amend the soil, and you shouldn't do that too soon in the year (again, depending on where you live.)