I frequently have people that are planning a first (or first in a while) trip to Disney ask for advice. Rather than repeating the same tips over and over again, I thought it would be easier to just create a document that had all of that info, and I could just send people a link.
There are lots of comprehensive guides to planning a Disney trip. This is NOT that. Instead, the goal here is to give you enough info so that you know where to put your focus, and I'll direct you to some other resources you can use when you're ready to dive into the details. There's more detail as you dig into the site, but if you really just want a thumbnail sketch, here's what you need to get started:
When you go will have a huge impact upon the crowds you are likely to see, and the amount you pay for tickets and hotel rooms.
Whether you stay at a Disney hotel or not makes a difference. Briefly, Disney hotel guests get certain benefits that other guests do not, but off-property hotels will be cheaper and more varied in terms of amenities.
Understand what the My Disney Experience app and Lightning Lane are and how to use them.
You can book dining 2 months prior to your arrival date, and if you want to eat at the more high-demand restaurants, you should take advantage of it.
To visit Disney parks these days, you should plan on getting your tickets at least 7 days in advance.
If you want to experience a lot of attractions and minimize waiting in long lines, the single best tip I can give you is to get to the parks 30-45 minutes before the park opens and be ready to hit the ground running. You can accomplish more in the first few hours the parks are open than late arrivers may do all day.
View this as a starting point, and let me know if you still have questions after you've read through everything. Finally, while I've created this with my friends and family in mind, advice is advice, so feel free to pass it along to anyone that might find it helpful.