if you are not sure do not invest, carefully study what they write about this project on the Internet, read the white paper with the team, etc.
Investing in cryptocurrencies is very risky one, it is not about being sure.
Either you are ready to take that risk or not.
When choosing a coin, u need to orient in the beginning to the team that is working on the project. It`s necessary to look at the roadmap when what events are planned. Of course, one of the main things in the project is the idea. U can also evaluate the potential of the project, comparing it with competitive projects.
First look at the project, read whitepaper and if project looks promising then research the team behind it.