Forget the online practice sites; they're a rip off. You can either pass the tests or you can't, and decent candidates will pass without any kind of practice. The best preparation is to polish your shoes, clean your suit and make sure you have all the documents they asked for. Then try to get some rest to be sharp. The interview questions are nothing unusual, though they ask for examples of when you have done something rather than hypothetical what if questions, so make a list of problems you have faced and how you dealt with them (you will be asked for a lot of detail).