I use Wanderlog, along with Microsoft One Note, to keep track of everything. Wanderlog is great for organizing everything and the proper dates. It keeps all the flights at the top, then it has a section for hotels and lodging, and then my itinerary, which I can fill in as needed. I love it because it adds photos, which makes it very visual, and once I enter everything in my basic itinerary, I can easily move everything around to make it more conducive to planning.
How it works is you create a trip by entering your destination and travel dates. Then you can look on Wanderlog for attractions, restaurants, etc., or add your own places that you found (WL will make suggestions of popular destinations). Wanderlog will then pull it from their database and give you something to put in there that has a link to the actual website of the attraction, times and dates, and even more information, including photos.
After that, you just start building your itinerary by dragging and dropping activities into each day of the trip. The nice thing about Wanderlog is that it has Google maps side by side with your itinerary, so that you can see exactly where your stops are on the map. This helps to plan your day more efficiently. You can also share the app with other trip members or your family so they can see where you're going to be. And you can use it on your phone or on your laptop. I usually create the itinerary on my laptop when I'm doing the trip planning because it's a bigger screen, but when I'm traveling, I have it open on my phone as needed.
The best part is that Wanderlog is free. There is a paid version, which I have, because there are a few extra features that I like, but you can pretty much do everything with the free version.
I also use Microsoft OneNote. CWSocial turned me on to that and now I'm hooked (we're both geeks at heart). I use that to keep all of my necessary documents and detailed information, so I can keep Wanderlog relatively uncluttered. It has everything in there, but if I want more detail, then I just head to the OneNote app and get it from there. I'm still trying to figure out a way to link them together more, but I haven't really found anything. But they still work pretty well, and I like using both apps together.