to pat (someone) on the back (to praise (someone))

E.g. 1:

A: You deserve a pat on the back for that speech. It was amazing.

B: Thanks. I’m glad you liked it.

E.g. 2:

A: Gillian’s boss gave her a pat on the back when she hit all her sales targets.

B: Yes, I heard that her boss praised her in front of everyone at the meeting yesterday.