You didn't say if you had park tickets or not so I'm not sure if our routine will apply, but here it is:.
The day we're attending HHN, we tend to sleep in a little later & have a relaxing morning and early afternoon. We get to the park around 3:00 pm and do some touring until it's time to go to the Stay and Scream area, where we wait for the event to begin.
Once we are released into the event, we try to hit as many houses as we can without using our Express Pass (usually not a problem because you are getting a good 30 to 45 minute head start on the masses waiting at the entrance, so it's not hard to stay ahead of the crowd and wait times are quite low at this point).
Once we've done that, the crowds are usually getting a little thick so we take a break, get a bite, and rest for a few minutes. This is a good time to see a show (we aren't Bill & Ted fans so we're looking forward to the additional show offerings this year).
Once we've revived, we do the circuit of houses once again, experiencing little or no wait time because we are now using our Express Passes.
After we've seen the houses twice, we might hit some rides but if the crowd level/drunkenness/rudeness factors are reaching intolerable levels (which they tend to do as you get beyond 10 or 11 pm), we just take off.
Enjoy yourself! It's a really fun event but, as others pointed out, definitely not for children!