Decide if and which tool you need
If you're a freelancer or own a small company where the team is very compact, chances are you don't need a tool at all. A whiteboard should do the trick, whether it's a virtual or a real one. Short daily or weekly meetings could also be helpful to know who's working on what. However, when large projects, teams, or companies are in the picture, problems pop up more quickly, and they're harder to solve. It's easy to misinterpret who's accountable, lose track of time and deadlines, misplace files, etc.
Do your homework. Explore, test, ask around, ask for advice. Don't be afraid to try out various tools and play around. Give yourself some time to weigh the pros and cons and make the final decision.