of course a good investor will first do its own research (whitepaper, roadmap and etc), besides that what is your biggest motivation?
Check how hype is the project and how many investors want to invest on the project. You can easily check it on the project telegram group, if many investor chat and talking everyday on the telegram and discuss about the ICO, it means many people want to invest and always invest on presale/private sale, because you can get big bonus.
These are the real factors which catch your attention to invest in bitcoin. It is also the rules of business to first investigate and scan the environment and then put your money. Without any research and analysis investing in a specific field could be risky as bitcoin is but it is also a fact that risky investment can give you more profit than normal.