1. Learn the general layout of the parks before you go ... or at least review them. WDW can be overwhelming for newbies and it helps tremendously to know the different "lands" within each park.
2. Get a general understanding of the transportation system (i.e., monorail, buses, boats, etc.). Most of us plan about a week for our WDW vacation and it can take several days to get used to the transportation route/possibilities.
3. Don't be a commando. Many of us planners can tend to pack our days by hitting all of the attractions we want to hit at break-neck speed and with little room for error. If you want to truly enjoy and appreciate WDW, give yourself some breathing room to "take it all in".
4. With that said, it is a good idea to decide which park(s) you plan to see on which day. This will help with the next tip.
5. Definitely make ADRs at soon as you can. When you have a general plan of which park(s) you will see on any given day, you can plan your sit-down meals (TS) accordingly. And don't be afraid to make an ADR if you are not completely sure of your plan. You can always cancel it at a later date. BUT PLEASE CANCEL if you plan NOT to use an ADR (an important courtesy to others).
Final tip/suggestion: DON'T STRESS once you are there. Remember that this is vacation! Don't freak out if your child is tired and needs a nap. Don't get angry if the person/group in front of you stops in the middle of Main Street, USA and halts your progress. Don't get mad if you just miss your bus to EPCOT ... there will be another one soon enough.
The last tip is something that I struggle with also - so please don't flame me for it! I have to keep reminding myself of this all of the time. But when I truly let myself enjoy WDW and suck up the magic, I am a very happy person
