keep a low profile

cobbler, keep to your last

One should not criticise matters outside one's field of expertise; one should mind one's business.

earn one's keep

To perform satisfactory physical labor or to provide other worthy services in return for remuneration, lodging, or other benefits; to support oneself financially.

fly low

To have one's fly (zipper) undone.

friends in low places

Friends who have underworld connections or are involved in shady underdealings.

hang low

To droop or sag heavily; to remain at a low altitude.

high and low

Everywhere; all over the place.

keep a civil tongue in one's head

To maintain a polite manner of speaking.

keep a close watch

to pay careful attention to a situation or a thing, so that you can deal with any changes or problems.