I don't set any stop losses. At the moment I only have companies in my portfolio whose strategy and operating business I understand and as long as nothing fundamental changes, I simply DCA when the opportunity presents itself. I would accept a 50% crash in any of my stocks. I think if you are so uncertain that you set a stop loss, you shouldn't buy the stock at all.
@Yoshika I agree, but for me a price drop is not an exit scenario. You always have to combine it with a negative change in the fundamental data and the cost of opportunity. Of course you should reinvest your money elsewhere if you are sitting on a melting ice cube.