You can only do so much and you're still not going to have 100% assurance of having a safe investment. Though of course your chances will considerably be better than those blindly investing on random icos without doing proper preparation but still, bottom line is there still are risks
You can invest safely in bitcoins for long term buy making correct use of your analytical skills and market intellect. People usually feel insecure because bitcoin doesnt exist physically and who will be responsible for their investments at the time of crisis, I think they will surely get answers to these when bitcoin will be legalized in the world.