Practical exercise
Pick a topic and debate a cousin both for and against
The fastest way to think well is to argue both sides of the same question on the same day. You will pick one debate topic, prepare for both sides, and run two short debates with a cousin: round one you take side A, round two you switch. By the end you will hold an opinion you can defend and a respect for the opposite view that most adults never earn.
Now try it
Pick a topic and debate a cousin both for and against
Stretch
Run a switched debate once a month for six months on six different topics. After six rounds you will have a stronger feel for your real beliefs and a list of topics where you genuinely cannot decide; both lists are valuable.
Goes into your portfolio
The folded prep paper, the signed one sentence verdict, the audio of round two, and a one paragraph reflection together as debate-both-sides-NN.