The Meguires Clay Bar kit is fantastic. Basically, you wash the car down as normal then dry off. Get yourself a bucket of nice warm water, break off a piece of clay the size of a £2 coin. Flatten out a bit, spray on the detailer working on a panel at a time and then proceed to rub the panel with the clay making sure that you keep the panel wet at all times. You'll feel when its drying because the clay will start to stick and then skid.
Clean your piece of clay in the warm bucket of water after each panel. Working on bigger panels such as doors/bonnet, do small sections at a time.
Sounds like hard work but its not really. Its very easy and once you've done it you'll love the finish that it gives. The paintwork feels like a piece of glass.
After claying, you must build the paint protection back up again and the clay has given the perfect base for a great finish. Use Meguires Stage 1, Stage 2 & then Stage 3. These are very good products to use. There are also other products and combinations but these are a great starting choice.
Matt and Simon (sjdickso) are worth contacting about this. They are also into detailing and know a variety of products available. It just depends like everything, how far you want to go and how much you want to spend.
;-)