do someone one better

an ounce of prevention is better than a pound of cure

Precaution and prevention of an undesirable thing is preferable to dealing with its potential consequences.

as best one can

In the best possible way, given one's circumstances and abilities.

as far as one knows

To the best of one's knowledge, as far as someone knows or possible information to be gathered about the topic, subject, aspect, or situation.

as if someone owns the place

Alternative form of like someone owns the place.

back to square one

Located back at the start, as after a dead end or failure.

beat as one

To share the same feelings.

beat someone round the ears

To beat (a person) with blows about the head.

become one flesh

To join together in marriage; to develop a unifying bond as a result of marrying.