Could

Yes, and both are really requests, not questions about ability.

What about: Can you help me? and Could you help me? and I wonder if someone can/could help me?

I always use 'could' when I want to be polite.

AnonymousI always use 'could' when I want to be polite.

That's right: that's the difference.

Will I be rude if I use 'can'?

Probably not.

I'm kind of starting to like your short and clear answers, MM.

I have another question( s ) that aren't related to the topic.

I hadn't had *** in ages. - Do I need to specify the second event in the past? I think that the tense tells us that.

Also, does 'can' work here as well?

AnonymousI hadn't had *** in ages. - Do I need to specify the second event in the past? I think that the tense tells us that.

Correct use of the past perfect requires some evidence of the second past event, either in the sentence or in the greater context.

AnonymousAlso, does 'can' work here as well?

Mister MicawberCorrect use of the past perfect requires some evidence of the second past event, either in the sentence or in the greater context.

So, I think I can say something like: I hadn't done it in ages. And yesterday I decided that it'd be a good idea for me to finally do it.

In this case the second sentence tells us when I did it, thus, makes

Yes, that's the general idea. The main idea is this: Do you need past perfect, or does simple past make it clear? Occam's razor: if you don't need it, don't bother.

Well, I know that I don't need past perfect when events are clear, BUT, this is not the case.

I hadn't done it in years, therefore, I can't say 'I didn't do it in years'. What do you think?