Here are a few key things to do before you set off:
Decide whether you will be going back more than once in the next year. If you are consider getting an annual passport instead of buying tickets for a few days. See the final chapter for more info on these.
Decide whether you want to stay on-site or off-site. On-site packages mean you get the hotel and your park tickets all for one price. Off-site usual means that you pay for the hotels and your park tickets separately - this may work out cheaper if you are not planning on visiting the parks every day. 
Get park maps before you go....
Click here to buy the guide for full access, including more details on what to do before setting off.