The DVD shown below will guide you through the stages required so you end up with the layout of your dreams. Peco also do a range of booklets covering all aspects of constructing and operating a model railway layout including wiring in great detail. The cost of the DVD is around £22 and the leaflet £1. (prices subject to changes)
Most manufactures of model railway stock have web sites and catalogues so make good use of them to see what is available taking note of sizes, colours, and of course price which you will need when planning.