Use one of these phrases to make polite requests:
▶ Could you (please)
▶ Would you mind
▶ I was wondering if you could

Here's how to form the sentences:

=> Option A: Could you + base form* of verb + "?":
Examples:
▶ Could you pick up a pizza on your way home from work?
▶ Could you help me translate this letter?
▶ Could you please** drop my book off at the library?

*The base form of the verb is the verb without any endings
** The "please" here is optional. Of course, it makes the request more polite.

=> Option B: Would you mind + [verb + ing] + "?"
Examples:
▶ Would you mind picking up a pizza on your way home from work?
▶ Would you mind helping me translate this letter?
▶ Would you mind dropping my book off at the library?

=> Option C: I was wondering if you could + base form of verb + "."
Examples:
▶ I was wondering if you could pick up a pizza on your way home from work.
▶ I was wondering if you could help me translate this letter.
▶ I was wondering if you could drop my book off at the library.

Note that Options B and C are less direct than Option A and therefore may sound a little more polite.