Get the car clean first with a bit of bargain basement car shampoo. Dry it with a chamois if you're feeling posh, then a coat of decent polish. I use Autoglym everything on the basis that if it's good enough for Rolls-Royce, it's good enough for me. What will really make a big difference is getting all the black nice and black again, and the chrome nice and shiny. Autoglym bumper care is amazing for the blacks, and, ahem, Brasso ain't bad for the chrome! A lot of people swear by respraying faded black bits with satin black too...
Only problem is, as you get each bit done, the other bits look worse, so you end up going at the paint again with more polish and wax, then redoing all the black, and so on....
