Same way I do in real life: I take a moment to ponder if what the person is saying has merit, review it and then thank the person for the info. If I can apply what the person has told me to do right away I will. If not, I'll just inform the person its gonna take me a bit of time to get used to it.

This is all assuming the criticsm is spoken at the very least in a neutral way. I'm not dependent on politeness. I just want civility.