Things to Consider...

 Compacted soil is bad

The soil surface needs to be loose enough that when you stand on the soil it will leave a footprint around 1/4” to 1/2” deep.

Getting rid of old grass and weeds

Kill out the grass and weeds that are now there to help clean up the weeds in the soils.  Remember after tilling to allow extra time for the native seed bank to germinate… so you can treat them before we seed.


Tilling the ground

Do you need to remove the grass entirely or just till under?  If you have an excessively thick mat of grass, it may be better to remove unless you are planning on grading some additional topsoil over it.  The grass can be clumpy when tilled.  Topsoil over the new lawn area can smooth this out if needed.
 

Soil amendments / organic matter

Most soils are lacking in organic matter.  This organic material is what helps feed the biology in the system.  You WANT beneficial biology working for you as much as possible… it makes growing things a lot easier.

Grading for drainage, contour, definition and functionality

Keep the grade draining away from key spots such as patios, ornamental ponds, house etc.  

Firm the disturbed area (to prevent future sink holes or valleys)

This can be done by a roller and landscape rake.  Check the local rental yard if your prepping the area yourself. Always finish rake or rough up the soil prior to Hydroseeding. 
 

Water requirements and scheduling

Automated irrigation systems are best.  You can set up the controller for frequent watering while establishing a new lawn.  If you do not have an irrigation system (and are not putting one in), then check out some of the new hose bib controllers on the market.
 

Ongoing maintenance program

Feed the soil and you feed the lawn.  Books have been written about keeping your mower blades sharp, aerating the soils, testing the soil for nutrients and on and on.  The basics are to mow no more than a 1/3 of the blade at a time, infrequent but deep watering as the grass plants mature and promoting a healthy growing medium.