These will all be followed by the verb in its base form.

Should is used when giving strong advice to do something.
You should teach children about emergency calls.

Would is used to express what you might do in a certain situation.
I would volunteer at the firehouse if I had more time.

Could expresses possibility and the ability to do something in the past.
There could be a problem if they don’t get enough volunteers.
I could run four miles when I was younger.

Another tricky string of letters is ould. The letter l is not pronounced, so ould sounds like ood. Could sounds like kood. Should sounds like shood. Would sounds like wood.

Americans sometimes use a funny expression to say that they wish they did something differently. They say, “shoulda woulda coulda.” Think things through before you do them, and you’ll never have to say, “shoulda woulda coulda”!