Trau, schau, wem!
Trust, but look at whom. The Duden explains it: one should look closely at a person before trusting him.
sich beschnuppern
To sniff each other, as dogs do. Two people or two groups get to know each other carefully.
mit jemandem warm werden
To grow warm with someone. One slowly comes to feel at ease with a person.
Vertrauen fassen
To take hold of trust. One begins to trust someone.
sich das Vertrauen erst verdienen müssen
To have to earn someone’s trust first.
erst einmal abwarten
To wait and see first.
Fuß fassen
To gain a foothold. One becomes established in a new place or a new job.
Anschluss finden
To find a connection. One is taken into a group.