How do you form the imperative in Spanish?

There are many different forms for the imperative in Spanish using the indicative and subjunctive moods and for informal and formal forms. 

Informal

The 'tú' form' 

Simply take away the 's' from the ending of the tú form in the present tense

Hablar - hablas - habla

Comer - comes - come

Abrir - abres - abre 

The 'vosotros' form

Simply take away the 'r' from the infinitive and add a 'd'

Hablar - hablad

Comer - comed

Abrir - abrid

Formal

For 'usted' and 'ustedes' use the present subjunctive 

Hablar - hable - hablen

Comer - coma - coman

Abrir - abra - abran

Therefore for the verb hablar you have:

Hablar

tu habla

usted hable

vosotros hablad

ustedes hablen

There are irregular verbs for the imperative!