I know it sounds dismissive, but I would get an Introduction to Logic and Reasoning textbook, and read it and attempt the problems. The internet is great, and you can get a lot from wikis, but you’re not going to beat the amount of useful info condensed into a book like that. The problems will also help you apply the knowledge. Also, since logic doesn’t generally change much over time, you don’t need to worry about getting the most up to date edition.
The only way to really get good at detecting fallacious arguments is practice.