He tried to chat her up at the bar.
chat up
idiomTo talk to (someone) in a friendly, open, or casual manner, sometimes also in a charming or affected manner, usually to curry favor, and sometimes flirtatiously with the intention of establishing a romantic or sexual encounter or relationship with that person.
The waiter spent too much time chatting up the customers instead of bringing our food.
The politician moved through the room with practiced ease, chatting up potential donors to secure their support for the upcoming campaign.