Pérate

This expression is utterly common and should be used every time the appropriate circumstances appear. Pérate (PE•dah•teh) is a shorter version of espérate, which is an imperative meaning 'wait' or 'stop it' depending on the context. Pérate usually comes in two forms.

Pérate-pérate is used to express confusion or lack of clarity in someone's ideas or speech. It is usually followed by barajéamela más despacio, which literally means 'deals the cards more slowly' and implies a request for a slower, simpler explanation.

¡Pérateeeee! is used when somebody is being bugged physically or verbally--typically a friend or a family member. It shows the subject is irritated and the next reaction might be physical aggression.

Example 1:

Lupita: Licenciado, acaban de llamar, que la grúa se lo llevó, y que el corralón está cerrado por el puente, y...
Lic. Fuentes: Pérate-pérate Lupita. Respira primero. Ahora sí. ¿Qué chingados le pasó a mi nave?

Lupita: Sir, they just called, the towcar towed it, it's in the pound, and it's closed because of the long weekend, and...
Mr. Fuentes: Wait, wait, Lupita. Breath first. Now, what the fuck happened to my ride?

Example 2:

Compañerito: Mochilas con los Pulparindos, no seas gacho, ándale, ándale... ándale
Pepito: ¡Pérateeee!... ¡Qué bien chingas! Si tus jefes no te dan camarón, ponte buzo con los cambios.

Classmate: Share your candies, don't be rude. C'mon... do it, c'mon.
Pepito: Drop it... Stop bothering! If your parents don't give you money you've gotta be smart and keep the change when you do chores for them.

Baras & Cariñoso

Baras (BAH • dass) and cariñoso (cah • ree • GNO • saw, lit. affectionate) are the best ways to refer to a price quote. Baras stands for barato, i.e. inexpensive. Cariñoso stands for caro, i.e. expensive. To add emphasis to any of them, precede them with bien pinche, which is equivalent to 'really fucking'.

Example 1:

Manlio: Se ve muy chida tu bírula. Te ha de haber salido en un ojo de la cara...
Fabio: Me salió bien pinche cariñosa. A ver si no me dan bajilla si la dejo aquí.
Manlio: That bike looks really cool. It must have cost an arm and an leg...
Fabio: It was very fucking expensive. I just hope nobody steals it if I leave it here

Example 2:

Vendedor en el tianguis: ¡Bara-bara-bara-bara-de remateeeeeee!
Marchanta: ¿De a cómo el mamey?
Vendedor: El primero se lo doy gratis, güerita. Del segundo en adelante a 10 pesos kilo, bien bara señito.

Street marker seller: Cheap-cheap-cheap-crazy-cheap stuff! 
Patron: How much for a mamey?
Street market seller: The first one is on me, blondy. From the second on it's 10 pesos per kilo, very cheap madam/miss.

Notice: (1) the use of bara as part of a quasi-chant to promote the products being sold; (2) the use of the  double-meaning of mamey by the vendor; (3) the use of güerita (blondy) as a way to flatter customers; (4) the use of señito in order to avoid mistakes using señora or señorita.

The image shows a tianguis (street market) seen from above.

Uuuta mano & Puta madre

When something terribly disappointing is revealed or takes place, an Chilango unconstrained by etiquette would exclaim ¡puta madre! (POOH • tah MAH • dre, lit. whore mother!) This expression is related neither to a mother nor to a prostitute  It's just an expression. The longer the u in puta, the more dramatic the disappointment conveyed. The variation of puta madre suitable for all audiences is uta mano. Mano is a short for hermano (just like bro is to brother). If instead of puta madre, one exclaims ¡putisima madre! the feeling conveyed is not disappointment but rage.

Example 1:

Personal de la aerolinea: Les anunciamos que el vuelo 822 con destino la Ciudad de Mexico partirá a las 10:30 de la noche y no a las 8:30 como estaba planeado. Mucho agrademos su comprensión.
Pasajero: Uuuta mano. Es la tercera vez que cambian el itinerario.

Airline personnel: Flight number 822 to Mexico City will depart at 10:30 pm and not at 8:30 as it was scheduled. We appreciate your understanding.
Passenger: Oughhhh! This is the third time the schedule is changed.

Example 2:

Comentarista: Este es el tanto que le dara el pase a la liguilla. El ariete se prepara, toma vuelo, conecta de zurda y ... ¡la volooooo!
Fanático frente al televisor: ¡Puuuuta madre!

TV commentator: This is the goal that can get them to the playoffs. The striker gets ready, takes a few steps back, kicks with the left leg and... he missed it!
Fan in front of the TV set: Fuck!!!

Example 3:

Celia: No me digas que fuiste por el hielo, las cocas, mas ron y se te volvio a olvidar el chingado limon.
Tito: ¡Putisima madre!

Celia: Don't tell that you went for ice, cokes, more rum and you forgot again about the fucking limes.
Tito: Fuck!!!

Cuba libre or just cuba is a highly popular cocktail in Mexico. Cubas without lime are lame.

¡Zafo!

Zafo (SAH • faux) is an interjection to make clear that a person does not want to participate in something. Zafo comes from yo me zafo, which means 'I set myself free' or 'I release myself from this.' 

Zafo is typically heard in a situation in which a group of friends are deciding who is going to do a chore (e.g. getting ice from the convenience store, opening the door when somebody is knocking and everybody is slacking, calling a pizza delivery place). Someone asks "who is going to do this?" and each of the present answers ¡zafo! It is agreed that the last person replying has the obligation to do the chore. When in Mexico, politely obey this unwritten rule.

Example:

(Family watching a soccer match)

Abuelo: ¿Quién va a cambiarle el pañal a Manuelito?
Abuela: ¡Zafo!
Mamá: ¡Zafo!
Hermanito: ¡Zafo!
Tía: ¡Zafo!
Papá: ¡Zafo!... ¡Chale! Está bien. Yo lo hago, pero al medio tiempo.

Grandfather: Who's gonna change Manuelito's diaper?
Grandmother: Count me out!
Mom: Not me!
Little brother: I'm out!
Aunt: I'm gonzo!
Dad: Not me!... Fuck! I'll do it. But let's wait until halftime.

Changing diapers can be a real drag. Practice your zafos before having children.

Cachirul

Cachirul (cah • chee • DOOL) is a term to refer to somebody who participates in an event (usually a sports one) without satisfying the requirements for participating. Such violation is typically done in secrecy and its ultimate purpose is to give the perpetrator an advantage.

Mexico's national sport, pambol, suffered international embarrassment because of the uncovering of cachirules playing for the national team against Guatemala in a qualifying game for the 1988 Olympic Games. Some players used fake birth certificates. As a result, el Tri couldn't participate in the 1990 World Cup in Italy.

The video below shows a very skillful 6-year-old playing soccer. The parents of the other kids surely thought he was a cachirul, a shaved-short dude.