Spend some time cleaning the wheels and tyres, it really adds the overall appearance of the car. Use a stiff brush on the wheels and try and get between the spokes.Get some 'wheel cleaner' from Halfords. Use some 'tyre shine' to bring the tyres back to a new appearance.
Once the body has been washed, dry the water with a large towel and then use a quick detailer spray and a couple of microfiber towels to bring a shine to the body.
Use house window cleaner on the windows.
Dont wash the car in direct sunshine. An overcast day is best. If the body gets too hot the products will flash off too quick and loose their impact and the water will evaporate, leaving streak that you will than have to polish off.
I wouldnt spend a fortune on car shampoo, unless your car is cleaned regularly, you wont see the benefit. If its really dirty, for the first wash , get some washing up liquid in bucket. Yes, its bad, because it contains salt - but it gets the job done and rinse with plenty of water and wash again with a suitable car shampoo.