Before any polishing I would recommend claying no matter how old the car is. All you need to do is trap ingrained dirt into the polish and all you are doing is moving it around the paint.
The basic principle of detailing is to strip existing protection (concentrated shampoo wash), remove anything contaminating the surface (clay bar), remove any scratches or swirls (polishing), fill or flatten the 'holes' from removing the contaminants (sp) (top polish / glazing), and to then protect the newly cleaned surface (sealant or hard wax). Then finally (or some do it as part of the protection) add a wax for a finish. Once this is done, the maintenance is about not letting anything get too permanently stuck into the paint with a regular clean (two bucket method, mild wash formula, minimum contact drying) and top up of the wax to finish.
There are all sorts of products out there. Dodo Juice seems to be the in thing at the moment (bit like Megs was a little while ago) and there are loads of others. Good quality detailing gear also comes under the names:- Chemical Guys, Zaino, Poorboys, Collinite etc. (others will have other names to hand!)
Pick a product for each of the stages, try it, see if you like it