There are many ways to learn about Guildford’s history. This web site is a good starting point as are the books you can buy or find in local libraries. Guildford Library in North Street has a good local history section.
For more specific research the Surrey History Centre, Surrey Archaeological Society Library and Guildford Institute are recommended.
Online resources include Exploring Surrey’s Past, run by the Surrey History Centre. This contains a lot of information on Guildford but for specific articles are also published regularly in the Guildford Dragon online newspaper. Guildford Past and Present Facebook page