Manual keyword research can be tedious and time-consuming, but it’s free! There are tools that give some basic results, such as the Chrome extensions mentioned in the lesson before this. There is also an online research tool that allows 2 free searches per day.
Below are several videos that show you how to do manual, profitable keyword research, but the best tool I’ve found for doing it all automatically is KDP Rocket (affiliate link). It’s not cheap, but it’s a one-off payment, rather than a monthly subscription, so that’s a plus!