If you apply some common sense, almost all scams can be detected easily, nothing is usually free. Yes I know giveaways exist out there but even those are not free, they usually require you to do some small task like retweeting something. Classic scams like: Hey I'll send you 1 BTC but you have to send me 0.01 BTC first, are clearly scams and if you fall for those, I don't know what to tell you.

ICO's on the other hand can be quite tricky. Obvious scammy ICO's exist and are easily detected but they are getting more and more sophisticated. It is really risky to invest in ICO's right now even if you do your research. Some ICO's have scammed in the past even though their team was real so that's not always an accurate way to determine whether the ICO is a scam or not.