This looks like a simple toolkit, but they are powerful tools and if you use this method you WILL become an expert in them.
Trip Advisor for selecting and documenting attractions, hotels, city overviews, restaurants; its forums for details Tell me more
Google Maps for finding where everything is, how to get from place to place, and how long it will take. Google MyMaps for capturing the details I want. Tell me more
Google search (or Duck Duck Go, or whatever) for details and advice, and event calendars
More about searching
Microsoft Word (or Apple Pages, or whatever) for recording it all, with lots of hyperlinking. Tell me more
A few specialist websites for reference (such as www.seat61.com for trains, www.seatguru.com for airplanes, Cruise Critic for cruises, airline sites and perhaps Google Flights to get an overview of flight options) Tell me more