CONDITIONALS:

ZERO CONDITIONAL: Real situation.

If clause	Main clause
If + Present tense	Present tense
If you freeze water	it turns into ice.

If I work too much, I get tired. 
Si trabajo demasiado, me canso.

FIRST CONDITIONAL: True or possible situation.

If clause	Main clause
If + Present tense	will / can / may / must + verb
If it rains today,	I'll stay at home

If it rains today, I'll stay at home.

Si llueve hoy, me quedaré en casa.

SECOND CONDITIONAL: Hypothetical situation.

If clause	Main clause
If + Past Simple	would / could / might + verb
If I won the lottery,	I would travel around the world.

If I won the lottery, I would travel around the world.
Si ganara la lotería, viajaría por todo el mundo.

THIRD CONDITIONAL: Hypothetical situation last

If clause	Main clause
If + Past Perfect tense	would/could/might + have + past participle
If I had won the lottery,	I would have traveled around the world.

If I had won the lottery, I would have traveled around the world.
Si yo hubiera ganado la lotería, habría viajado por todo el mundo.