These usually work:
Would you like me to take that?
Can I take that for you?
Can I take your plate?
For extra politeness, you can use "may" or "shall" instead of "can". You can also add "sir" or "ma'am" to the end of your sentences as a polite form of address. If you need the preposition, use "away" - not "out".
May I take your plate away?