I got my LRPS a while ago and can really recommend having a crack at it.
There's no particular recipe to producing a panel of prints, and the variety of work i huge, but as a guideline you need to demonstrate a good level of technical ability in a variety of situations, using a variety of techniques. What the judges want to see is that you have an eye for a good image, and the ability to choose the correct techniques to produce a an image that looks good in print.
As a starting point download the guidelines from the RPS website, and try and attend an advisory day.