Yard Guys- How do you Prep for Grass?

I don't mind working in the yard, I'm just not very knowledgeable about how to do it!!

About a third of our backyard has never had grass. Weeds grow 5-6 feet high before we go out and cut/pull the weeds. We want to get to the point of having grass.

Is there a process to go from what we have to grass? I was thinking of spraying grass and weed killer now, then in the spring rototill it, smooth it out, and plant grass seed.

Any other ideas? Thanks!