Indentation should be done with tabs. However, after a character that's not a tab, i.e. any printable character, spaces should be used. It is the best of both

Indentation should be done with tabs. However, after a character that's not a tab, i.e. any printable character, spaces should be used. It is the best of both worlds, and can never be misconfigured by changing the number of spaces that a tab represents. It is also what tab advocates have been saying for years now.