Here's my tip: some credit card companies let you create virtual credit cards. You can often set them with a custom expiration date, so set the date to tomorrow.
My wife is so bad about this. I tried to explain to her that for many of the services you forgetting about the subscription is their whole business model.
I have an old coles mastercard gift card with only $4 left on it for this exact purpose. They can test it with a $1 temporary charge but it won't cover the full cost at the end of the trial.