TÚ commands, also called informal commands, are conjugated in two different ways depending on whether you're saying a positive or negative command. The formula is:
Verb | POSITIVE COMMAND | NEGATIVE COMMAND |
beber | bebe | no bebas |
jugar | juega | no juegues |
almorzar | almuerza | no almuerces |
If the verb is reflexive, you have different rules for the reflexive pronoun depending on whether it's a positive or negative command.
Verb | POSITIVE COMMAND | NEGATIVE COMMAND |
acostarse | acuéstate | no te acuestes |
despertarse | despiértate | no te despiertes |