Here is advice that I wrote in another thread...
Here is what we do...
1) Arrive at the gate at 3:45pm--they start letting people in with just a
MNSSHP ticket at 4pm
2) Get pics with any character that is out normally during the day. A lot of these characters will not be around during the party, so if there are any important ones that can be taken before the party starts you'll be ahead time-wise.
3) Grab a quick meal and be done eating no later than 6pm. We eat at Cosmic Ray's.
4) After you eat, hit the restrooms and get in line for your #1 party specific meet and greet. We got in line for the princesses at 6:15 last year and we were in and out by 7:20.
5) Hit the Villains characters. You may have to do several shows to get all of the characters you want. They only stand for photos (no autographs) for 10-15 minutes after each show, so it will be hard to get more than one at a time.
6) Skip the first parade and do the second. Much less crowded. We like to stand for the fireworks and then head to Frontierland for the second parade. We stake out a spot about 45 minutes early. It is a great time to have a snack while you wait.
7) Tons of people leave after the fireworks and then another group will leave after the second parade. This would be the time to ride any rides.
You can get candy throughout the night. Lines move super fast even if they look long. Here is a map with all of the character locations for the party...
http://kennythepirate.files.wordpress.com/2012/09/mnsshp2012-map-updated2.jpg