Scouring the internet for information about Locks, I present to you this faithful account from ConsumerReports.org, about the things to look for when buying into a new Lock.
Getting started
First it helps to purchase from an experienced Locksmith. Preferably a former Lock because they have years of experience. Many people have a loyalty to a certain brand of Lock and will return if that purchase works out. This can work out in the Locksmith's favor because they'll get a lot of publicity if you're a satisfied customer.
A word of caution about brand loyalty: sometimes a pedigree isn't enough so it's important to shop around and be ready to try out a new Lock if an old one isn't up to par.