Which methods, technics and languages should I use to develop a price comparison site

I would like to know all about programming/developing a price comparison website.

Which is the main solution and process to get information about products (could you explain)? Which Strategy to adopt to get my database up to date (may be each day)? Which architecture and languages or frameworks could one recommend me?

I don't know enough about this topic, please I need help in order to develop such a solution.