if I think personally a safe way to invest in cryptocurrency is :
1. the project runs according to the roadmap and whitepaper that has been made;
2. cryptocurrency that we invest in already has a product;
3. the team always updates about the progress that is happening in the project that we invest;
4. invest in project that are in the top 1-500 in coinmarketpcap (have a high volume);
5. the project we want to invest has been running for a long time (if I personally never invested in a new project), because investing in new project has a greater risk than we invest in old project.
Investing in new projects is very profitable if you find the right one. But you invest in a bad project that is the place where you will lose money. I think it is better to invest within the top 200 coins in the market instead of within the top 500 altcoins. Top 500 altcoins are way too many, you could fall into scam coin easily.