Depends if you want a lawn, or like me, want to get rid of it !!
If the grass is dry enough in a couple of weeks, set your mower on its highest cut and start at that point. As it warms up you can slowly drop the blades to a nice 1/2" swathe, sprinkle lawn sand (if you have moss) and growmore to feed it. Aerate it with a fork (poke holes in it), rake it with a lawn rake every other month and cut twice a week when it really starts growing and watch your neighbours go green with envy