It wouldn't hurt to stick a fork in and work it across the area you want to seed, just to aerate the soil; rake it up/down then left/right to work out any large stones, maybe add a little liquid feed and perlite. If you dig too deep you'll end up with a raised level.
What's the drainage like?
You may need to raise the level above the yard to help the grass roots get all the moisture rather than water sitting on top.
Once you've planted make sure you don't walk on the surface for a few months and cover it with fine mesh netting - otherwise the bloody pigeons will treat it as a snack bar!