You will get a bunch of replies to this post, no doubt, but these questions are asked several times over. I suggest you do a search of the forum and go from there.
Some of the highlights you will get is:
Plan, Plan, Plan.
Do research...go and by a touring guide. Touring Plans is a great resource.
Get to the parks at rope drop.
Avoid the autograph lines to start your day and get to the attractions.
Utilize Fast Pass...it's a time saver.
Utilize Extra Magic Hours if you stay on-site.
Stay away from EMH parks if you are off-site.