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....
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Click here to buy the guide for full access, including more details on what to do before setting off.