I did my PPL skills test on a C152 last year. It is best to know your POH inside out but if you are not sure of something just tell the examiner that you don't know but you can look it up in the POH. Once he/she knows that you can find the answer in the POH they are happy.
Do know your speeds, weights and take-off/landing distances.
My test was also over 2 flights as my examiner was a heavy guy so i had to come back and refuel before doing the circuits!
At the end of the day the examiner just wants to see that you are safe and not going to get yourself killed so just relax and try and enjoy the test. If you do anything wrong just keep on flying and forget about it.
Best of Luck.