I have a good friend that I travel with and once we determine a destination or general area, we create a Google Sheet and start filling it with ideas/things to do that we found on the internet. I also fill out the sheet with a bunch of flight and hotel options using miles/points (I probably do too much, but I get really excited so I like to see what all is available). The Google Sheet is great for sharing with your travel companions and then you have 1 go to place for all the things you found interesting on the internet and all the planning. The flight options that I record are also great since we are using miles and sometimes flights on certain airlines/routes/cabins can be hard to get, so it helps to know all the options and with piecing together the itinerary.

As for what to do once you get there, I prefer a mix of guided tours/activities and wandering on my own. I like to try to do a guided tour/activity early on in the trip because it helps to get an understanding of the area, I can see places that I might want to visit after the tour, and I like to talk with the guide and other participants about the culture, area, and to try and get some local suggestions.