I know whitepaper should be the first thing you look at for an ICO but it is one of the last things I check before I invest.
I definitely think it is crucially important and I do not mean last thing I check in importance, it is definitely as important as anything else, I just mean last thing as in the sorting of it. I prefer to check the public hype before anything else.

If there is hype about a coin that is coming up the next thing I usually look at the team that is developing the coin and if I heard of any of them before, I mean if vitalik came out with a new coin we would all join probably.

After those are done I check the whitepaper and see if it is fixing any problem that needs a vigorous immediate solution. Last time I did all of them I purchased few coins and that didn't work for me so this is not a guarantee it will work for all the investors and all the times. Investing in cryptos is slowing moving toward a point where people simply risk their hard earned money in the name of gambling.