It depends on the project.
At first, I look at the website and if that checks out, I start reading the whitepaper and researching the team.
Like, are the team members real people who are what they are advertised as on the homepage?
Do the team members have personal social media accounts which confirm that they are involved in the project?

Is the whitepaper written in a good manner?
Do the token economics make sense, so not too much premine and not too many coins held back for sketchy reasons?
Are the projected numbers viable or do they say something like "we will grow 100% each month after ICO"?
Do they have a roadmap and how detailed and believable is it?

So this complete process sure is time intensive.
When I am screening for new ICOs I spend about 30mins on the initial stage.
Afterward, it differs because of factors like length and complexity of whitepaper, the number of team members I have to research and if applicable additional knowledge of targeted industries I have to obtain to assess the ICO proposal better.

So if it is a complex project that I want to invest in it takes me probably more than 10 hours.
I just like to know WHAT I throw my money at