I don't think there is a perfect solution for this, but this site has various very good posts about the topic:
###Key lessons learned (the TL;DR version):
- users are easily able to find translation links in footers
- language names work well at communicating links to translations – but only if the user is familiar with that alphabet (for instance, as English-speaking user won’t recognize Chinese lettering if Chinese is the current language)
- the use of flags do not aid users more than listing language names and using other iconography for selectors
- be careful when using online remote testing. Careless participants can skew your outcomes
