Well, you have a look at the local papers, see who is selling interesting looking places, and pick an agency. Which agent (person) you get is usually the luck of the draw. And if you get bad vibes/feel uncomfortable/whatever, you believe those vibes, walk out the door and into the next one.

Or you can ask your friends/family who have bought places if they recommend the agents with whom they dealt.

Or I can give you my mum's details, if you're looking in the Bayswater/Bassendean/Morley/that Midlandish area. At least you know I can vouch for her.