During the client meeting if the meeting will continue after I leave(Note-my part is over in the meeting) what shall one say to all? Should I say “I shall take a leave”? what is the correct usage of the idiom. Please help me.
I usually say something like, "I think my part is over, so if you'll excuse me ..." And then, as Cagey suggests, say whatever is appropriate about nice to meet someone or look forward to seeing you later or look forward to working with you or if you need me you're welcome to call or email ... really, whatever is appropriate for the moment, considering whether it's a new client or a long-time client, whether you know everyone or just some of the people or they're all new. It will also depend on your rank in the meeting -- if you're the lowest-ranked person, you should avoid the long speeches and excuse yourself with as little fanfare as possible.
For some reason, "I will take my leave now" sounds a bit grand to me, only a step away from "I shall now take my leave."