1. team behind the project?
2. type of blockchain?
3. real-world use-cases?
4. partnerships?
4 points above is what I always see before investing in altcoins and besides that I also see whitepaper so that I know more about the objectives of the project
being able to analyze whitepaper and see whether the project is really serious in technical aspect is good but as far as it goes if the project isnt interesting for people and failed in fundraising the whitepaper will be useless i will always see the people behind the project first because thats the biggest factor.