Photographers know, that the most important part of focus is focus on the eyes. There are certain cases of course where creative approach is taken and it shifts. But when talking about photography we are always talking about rules of thumb that are there for guidance for best general result and can, or i should say must be always broken once you know them.

So focus on the eyes. If you subject is directly in front of you which eye would you focus on? Left or right? Correct! Both of then at the same time, since they are at the same distance.