There's really no absolute way to check if something is a scam. This is a very new industry and isn't regulated like many traditional investment vehicles.
Really, participating in an ICO is like being an early-stage investor in a start-up. You absolutely MUST do a LOT of due diligence. Study the founders, study the whitepaper, study the target market.
People are irrationally exuberant about crypto right now and it is going to bite them hard. Right now, cryptocurrency is where the internet was in 1997. Everyone thought that throwing money at any stock that had a ".com" in the name was a guarantee to make money. And it was... until it wasn't...
So you need a strategy that you are personally confident in. Personally, I stick with an industry I'm competent in. That way I already know the big players, the industry, and have a better "nose" for sorting the good from the bad. I'm an avid online gamer and computer game nerd. So, I follow a lot of projects in that space. After studying them A LOT, I have a running list of projects that I'm interested in.
My current list is:
www.enjincoin.iowww.MindSports.IOwww.waxtoken.comwww.playkey.ioI came by that list with a LOT of hard work, and continue working very hard to add to that list as I have time and energy to dive into the research. If you just go off half-cocked and start investing in ideas after an hour of research, you'll lose your shirt.
Best of luck!