How do you plan your travels?

Hey there, beginner traveller here, I was appointed to make the travel plans (itinerary, budget, etc.) for a family trip.

I’ve never had to plan a travel before since I usually just wing it when I travel.

How do you normally plan your trips? What tools do you use? How do you organize your plans? And how do you decide which places to go or not?

Any other tips would also be greatly appreciated!