None of the examples you give need the -ing form. 'Not watch TV' is not the right imperative form. It should be 'don't watch TV'. The second example can use the bare infinitive - 'You should help your brother, not just sit there' - because 'should' goes with both 'help your brother' and 'not just sit there'. 'Tell her to not live apart like this' isn't the usual form either - 'tell her not to live apart like this' would be more usual. Or it may be addressed to the friend, not the woman: 'tell her to move back in; don't live apart like this'. So the correct versions are: - If you're not going, then wash the dishes, don't watch TV. - You should help your brother, not just sit there. - If you still love her tell her to move back in with you, and not to live apart like this. OR - If you still love her tell her to move back in with you. Don't live apart like this.