Good morning and welcome to Namepros. I wish you good luck on your journey.
This is what I did.
Set up a basic spreadsheet on excel.
Google to find list of all extensions new and old. Go to Godaddy and find list of all domain extensions that they provide for registration.
Copy and paste these lists to spreadsheet. Once you have the list available to view all you need is your imagination. Find things that interest you and things that you know are selling at the moment.
Do not do what most new people do which is to join two random words together to make a dot.com domain name as most of the time that will not make sense.