Before investing in altcoins, you should look at the team working on the project. and also read the whitepaper or see the project roadmap.
I do all this things and thorough research before it guarantees me that this project in future will be successful. Also another thing is that will that coin have a demand in the next 1 year and what will drive that demand due to which coin will have a high value . Once this questions answers you then you are good to invest in that project.
That's right! You don't need to ask anyone, ask your-seft the reason make you should invest in altcoin. Beside that, research others still buying this altcoin or not. This is also a base to help you easily seach the reason made them bought this altcoin.