Use Dawn dish washing liquid to wash it. Dawn will break down and wash away any existing wax.
Then use a Clay Bar to deep clean and get rid of all surface contaminates. If you've never used a Clay Bar, you'll be impressed at how smooth your paint is after you use one.
Wax from there and this is where you are going to get MANY opinions.
Lately I have been using Mequiar's Ultimate. I use to be a Zaino guy and the results were awesome but there are quite a few steps to Zaino and it literally would take all day. Looking to make things a bit easier I started reading many reviews and Mequiar's Ultimate was always being compared to Zaino. Since it is about 1/4 of the price I decided to try it and I have to say that I am very happy with it. I won't say it is exact to Zaino but it is pretty darn close with just one coat.
Another popular one that I see is Collonite 845. It was not created in the beginning for cars, it was created for the electrical industry but the car industry loves it. It goes on real easy like the Mequiar's Ultimate. Collonite also makes 476 in paste form that is supposed to last a year, whereas 845 says for 5 months.
There are many other solutions but it does start to get pricey like Cquartz and Optimum. The process to use them should however be left in a professional's hand unless you really know what you are doing when it comes to prepping paint.