The Conditional Perfect Tense follows the same pattern as all the other perfect tenses of Spanish.  We can use the conditional perfect when we want to indicate what 'would have happened'.  We can also use the conditional perfect tense to indicate conjecture.  If you want to speculate on 'what must have happened'  or 'what time it must of been' for example, you can use the conditional perfect.   In most conditional perfect sentences you will have an 'if' or a 'but', either stated or implied.  The conditional perfect is a good way to make an excuse for something in Spanish.  For example, "I would have written this article sooner, but I have been lazy".  

As you may recall all perfect tenses have two parts.  It starts out with a conjugated form of the verb haber (to have done something), and a past participle, (done, used, closed, opened, found, lost, etc.).    But when indicating what would have happened, like, "I would have written this article sooner, BUT, I have been lazy", you have to explain what the 'but' or the 'if' is. In this example the 'but' is explained by the true fact that I have been lazy.  We will look at how this example translates to Spanish later.  

You might like to review the articles, "A Very Perfect Tense", "Your Future Is Also Perfect" and "Perfect Spanish Uncertainties".  Remember the only difference between all the perfect tenses is the respective conjugation of haber.  The past participles are all the same.  The additional requirement for the conditional perfect is having to explain what the condition is.  

First, let's look at the conditional prefect's conjugation of haber:

Habría - I, you, she, he, it, (formal, usted) would have.
Habrías - you, informal (tú) would have.
Habrían - They would have (ellos).
Habríamos - We would have (nosotros).

Now here are a few examples of the conditional prefect's  conjugation of haber joined with a past participle to form a sentence:

I would have gone with you,  but I was tired. - (Yo) habría ido contigo, pero estaba cansado.

She would have eaten, but she wasn't hungry. -  (Ella) habría comido, pero no tenía hambre.

We would have seen it, but it was dark. - Lo habríamos visto, pero estaba oscurro.  

I would have written this article sooner, but I have been lazy. - Habría escrito este articulo más pronto, pero he estado perezoso.  

The first three are easy.  Just the conditional perfect conjugation of haber with a past participle.  Notice the 'but' condition being explained by the imperfect tense.  If you would like a review of the imperfect tense, I suggest you read the article "A Not So Perfect Tense".  However, the imperfect does not always have to be used to explain the 'but' condition.  For example, did you notice the last example above combines two of the perfect tenses.  "I would have written this article sooner" (the conditional perfect), but I have been lazy" (the present perfect).  

Now for a few examples of the conditional perfect with an 'if'.  OK...  For students that have been at Spanish for awhile,  the 'if' should trigger thoughts about what? Yes.  The subjunctive!  When it comes to an 'if' being included in a conditional perfect sentence, the past subjunctive is used to explain what it was. If you would like review on the past subjunctive, I suggest you reread the article "Past Hopes, Desires, and Uncertainties".  
If you are unfamiliar with the subjunctive tenses,  you can still use the conditional perfect.  Just memorize the examples below.  And let this be kind of an introductory lesson.  

The 'if' implies a condition that may or may not happen, or have happened.  Classic conditions for a subjunctive sentence.  

Anyway,  here we go with a few conditional perfect examples with an 'if' involved.

Would you have bought it if you had your credit card? -  ¿Lo habría comprado si tuviera su tarjeta de credito?

She would have gone to Panamá if she knew how to speak Spanish. - Habría ido a Panamá si supiera hablar español.

Would you have done it if you had another chance? - ¿Lo habrías hecho si tuvieras otra oportunidad?

Just remember if there is a 'if' in the conditional perfect sentence, it will require the past subjunctive to explain the condition.  If there is a 'but', you will use the imperfect or the simple past (preterate), or even the present perfect.  

Now let's look at a few examples of the conditional perfect being used to indicate conjueture.

He must have gone.  -  Habría ido.
She must have done it. -  Lo habría hecho.
It must have been 5pm when it hapened.- Habría sido a las cinco cuando pasó.
I suppose that she left. -  Se habría ido.   Note that 'ir' means to go, 'irse' means to leave.  'Ido' is the past participle of ir.  
It must have been March when she bought it. - Habría sido el marzo cuando lo compró.

So, to sum it up,  the conditional is basically just like all the other perfect tenses.  Learn the conjugated form of haber, and become familiar with as many past participles as you can.  When you learn a new Spanish verb, learn its respective past participle.    And then remember if there is an 'if' condition,  it is explained by a verb conjugated in the past subjunctive.  

There are other tenses in Spanish that are used to express would have and conjecture statements.  But learn this one first and you will add another valuable tool in your quest to speak and understand better in Spanish.  And always, practice in live conversation and keep it fun.

Hope this helps,