How do you form the negative imperative?

the negative imperative can be formed one of 4 ways: 

a) With ne (nemo, nihil, numquam) + perfect subjunctive, when indicating a harsh command. eg: Ne timueris! = Do not be afraid

b) with noli, nolite + present infinitive, when indicating a softer command. eg: Noli ridere, quaeso. = Please do not laugh.

c) With fac, facite; vide, videte; cura, curate ne + present subjunctive, when indicating a warning. eg: Vide ne proficiscaris.= See to it that you do not leave!

d) cave, cavete (with or withoug ne) + present subjunctive, also to indicate a warning. eg: Cave dicas hoc. = Do not say this.