Would signals distance from real, direct wording: imagined, softened, or reported. For polite requests, reach for would whenever you want someone to do something and want to sound less direct than will: Would you make dinner tonight? sounds softer than Will you make dinner? The same distance from real, direct wording also covers unreal plans, past routines, and reported speech.
Your situation decides the wording
Imagining something unlikely. When you picture a situation that probably won't happen, would goes in the main clause, not the if-clause. If we went to Chile, we'd have to go to Argentina as well. The if-part stays simple past even though you mean now or the future. The past form signals distance from reality, not past time.
Telling a story about routine in the past. If you're narrating repeated past actions, would fits. We would meet every Thursday morning and plan the week. Keep it to actions and events; it sounds natural in formal or narrative style. For past states like I used to live in Melbourne, would doesn't work, since living isn't a repeated event.
Reporting what someone said about the future. If the original words used will and time has passed, backshift changes it to would. Compare direct speech, I will call you tomorrow, with the report later, She said she would call me the next day. The will becomes would because you're relaying earlier speech, not as a standalone rule.
A quick habit check before you commit. Ask whether the sentence describes something that actually happened repeatedly in the past. If yes, and it's an action, would works. If it's a state like living somewhere or owning something, reach for used to instead.
When the situation is real and likely, drop would. For a genuine possibility you expect to happen, say If it rains, we will cancel the picnic. Would belongs to the imagined or unlikely version, so a realistic plan needs will instead.
One habit check before you commit
In storytelling and formal writing, would sounds right for repeated past actions. We would meet every Thursday morning and plan the week fits a memoir or a written account, where the rhythm of would carries the narrative along.
In a casual chat with a friend, the same sentence often feels more natural with used to: We used to meet every Thursday. Both are correct here, so pick by how formal you want to sound. If you're unsure which register you're in, used to is the safer everyday choice.