Unreal? Use would in the result clause: If I won the lottery, I would buy a house.
Polite request? Would you mind taking my photograph?
Real past? If it was raining, I stayed inside.
After if, say were, not was, in these hypotheticals
When your if sentence imagines something unreal and the verb is be, use were after if, no matter who the subject is. Then put would in the result half: If I were rich, I would travel more. If she were here, she would help us.
It sounds odd at first, because you'd say I was when talking about the real past. In an unreal condition, though, were signals that the situation is imagined, so it pairs naturally with would in the other half of the sentence.
In everyday speech you'll hear If I was you, and nobody's confused. If you're writing something formal, like a job application or an exam answer, stick with were: If I were the manager, I would change the schedule.
Quick check for this case only: when your if clause imagines something unreal and the verb is be, choose were. Compare If it was raining, I stayed inside, a real past situation, with If it were raining, I would stay inside, an imagined one.