SHOULD

Is a modal verb, we use it whit other verbs to give advice.

Afirmative form:

We use should with everyone without changing its form.

Subject + modal verb + verb infinitive without to

Example:

he should work harder.
You should tell Miss Gómez the Truth.
They should leave as soon as possible.
She should be doing her homework.
Pedro should exercise more.

Negative form:

We use should with everyone without changing its form.

Subject + modal verb + not (shouldn’t) + verb infinitive.

Example:

You should not say that.

You cau use the contration the should not = shouldn´t. example:

We should not arrive late. = We shouldn't arrive late.
Carolina should not be working. = Carolina shouldn't be working.
It should not take long. = It shouldn't take long.

Interrogative form:

Should + subject + verb infinitive without to.

Example:

Should I study this chapter for the exam?.
Should I write Alvaro a letter?
Should we worry?

SHOULD + HAVE:

To talk about the past we used should add have.

Example:


You should have told me you were going to arrive late.
Graciela should have consulted me.
I shouldn't have eaten so much.
Camilo y Daniel should have waited for you.

http://www.englishgrammarsecrets.com/should/exercise1.swf