Spanish Idioms

The following are more common Spanish idioms that will help improve your ability to converse in Spanish and improve your fluency.
English
Spanish
It is raining cats and dogs
Llueve a cántaros
(literal: It is raining pitchers)
Birds of a feather flock together
Dime con quien andas y te diré quien eres
(literal: Tell me with whom you walk and I'll tell you who you are)
You can't teach an old dog new tricks
El loro viejo no aprende a hablar
(literal: The old parrot doesn't learn to talk)
A friend in need is a friend indeed
En el peligro se conoce el amigo
(literal: In danger the friend is met)
You reap what you sow
Se cosecha lo que se siembra
(literal: What you sow, you will harvest)
It is the early bird that gets the worm
A quien madruga, Dios le ayuda
(literal: God helps he who wakes up early)
A bird in the hand is worth two in the bush
Más vale un pájaro en mano que cien volando
(literal: One bird in hand is worth more than a hundred flying)
You make me crazy
Me vuelves loco
(literal: You make me crazy)
Out of sight, out of mind
Ojos que no ven, corazón que no siente
(literal: Eyes that do not see, heart that does not feel)
You can't please everyone
Nunca llueve a gusto de todos
(literal: It never rains to everyones liking)
The best things in life are free
Lo que no cuesta dinero siempre es bueno
(literal: What does not cost money is always good)
We all make mistakes
Él que tiene boca se equivoca
(literal: He who has a mouth makes mistakes)
You never know what you have until it's gone
Nadie sabe lo que vale el agua hasta que falta
(literal: Nobody knows how much water is worth until it's missing)
If you keep your mouth shut, you wont put your foot in it
En bocas cerradas no entran moscas
(literal: In closed mouths, flies don't enter)
Necessity is the mother of invention
La necesidad agudiza el ingenio
(literal: Necessity sharpens ingenuity)
Look before you leap
Antes que te cases, mira lo que haces
(literal: Before you marry, look what you do)
Is the coast clear?
¿Hay moros en la costa?
(literal: Are there Moors on the coast?)
Brain is better than brawn
Más vale maña que fuerza
(literal: Skill is worth more than power)
Think before you speak
Antes de hablar, pensar
(literal: Before speaking, think)