I agree with you, if anyone likes the sports, and understands the odds, it's enough for placing bets! It's so simple... people talk about researches and knowing the sports, but most of those things you can find online, with following a few bloggers you can get into it without much trouble.
So probably the best answer is to bet on the sport you like! It's easy to check more about the sport itself and to find people who are into it and follow them, but that is possible only if you have an interest in a specific sport and you have a desire to read about it and follow it.