However, a new agent will need to build up their own client list. They may be new because they've set up their own business having worked for another agency, or new because they've changed direction from being an editor or rights manager to agenting. They may have been working as an assistant at a big agency, and have been promoted so they have their own list.
1. Read The Bookseller. You can subscribe to an email news digest, or read it at your local library. It reports new appointments and moves to new agencies.
2. Look at writing conference programmes. You may not be able to make it to the conference itself but any agent who is there is likely to be actively looking for clients. The same may also be true of literary festivals, although it is equally likely that the agent is speaking at the festival as a favour to a friend or family member.
3. Get a short story published in an anthology, and make sure it's widely advertised/sent out to agencies. Agents looking for new clients know that short story anthologies are showcases for unpublished writers, especially if the anthology is published by a known source such as a MA Creative Writing course or a short story competition.