Examples:
If you don't read The Smiling Eggplant regularly, you'll regret it.
If I were you, I'd read The Smiling Eggplant.
If he had faithfully read The Smiling Eggplant, he would have enjoyed his trip to Italy more.
Now. Here is my own personal, somewhat simplified, scheme of these pesky but essential sentences.
Hypothetical of the First Type, which I call the Real Hypothetical. The easiest one. If This, then That. The If clause will usually have a present indicative, the other clause will have a present (sometimes with a future meaning) or a real future indicative.
Se studi, passerai l'esame.
If you study, you'll pass the exam.
Se mangi troppo, ingrassi.
If you eat too much, you get fat.
Vieni a vedermi se passi da Milano.
Come see me if you come to Milan.
Easy? Hah. But of course it gets more complicated.
Hypothetical of the Second Type, which I call the Unreal Hypothetical. Unreal, or at least unlikely. Here, the If clause will have the imperfect subjunctive, and the other clause will have the conditional.
Se fossi in te, non sposerei Carlo.
If I were you, I wouldn't marry Carlo.
Abiterei a Nantucket se avessi i soldi.
I'd live in Nantucket if I had the money.
Cosa faresti se ti si bruciasse la casa?
What would you do if your house burnt down?
It gets worse. Here comes the Third Hypothetical, which is just the Second Type in the past. I Call it Unreal in the Past. This is really Unreal, since the condition expressed in the If clause has passed; therefore, the result is impossible. It takes the trapassato of the subjunctive in the If clause, and the past conditional in the other clause (sometimes just the simple conditional.)
Se avesse studiato di piu', avrebbe passato l'esame.
If he had studied more, he would have passed the exam.
Non me ne sarei andata se non mi avesse insultata.
I wouldn't have left if he hadn't insulted me.
Se avesse fatto piu' moto da giovane, adesso starebbe molto meglio.
If she had been more physically active when she was young, she'd be much better off now.
So there are two important parts to mastering this important feature: one, you must correctly understand the usage of each type and use it appropriately and two, once you have identified the usage, you must know the correct form of the present indicatives, future indicatives, imperfect and past perfect subjunctives and (whew!) conditionals.
Coming up later this week: exercises on hypothetical sentences.
If I were you, I'd do the exercises.
Se fossi in voi, farei gli esercizi.
