In most cases, the conditional is used in conditional clauses, polite requests and questions:

I would like to go watch the game tomorrow.

In addition, the conditional clause can include an auxiliary verb could, should, ought to or might:

You really ought to take better care of your belongings.

The present conditional takes place in the present moment but the verb is in the past tense in the subordinate clause. Formation of the present conditional: in the main clause would/could/should/ought to/might + base form (Would you consider) and in the subordinate clause the past tense (offered):

Would you reconsider our offer if we offered you a better deal?

The negative conditional is formed by adding not after an auxiliary verb and it is often shortened n’t: You shouldn’t believe

It is also possible to use the past perfect in the subordinate clause with the present conditional in the main clause (hadn’t struck). This form is used when you want to tell about the effect of a past event on the present:

If a meteor hadn’t struck the earth millions of years ago, dinosaurs might still exist.

Note that would and should can also appear in the subordinate clause in some cases:

It would be nice if you would take the dog out.

If something should happen, would you be so kind to contact me as soon as possible.

The past conditional is used when telling about something that would have happened. Formation of the past conditional: in the main clause would/could/should/ought to/might + have + 3rd form of the verb (might have achieved) and in the subordinate clause the past perfect (had kept):

You might have achieved your goal faster if you had kept on track.