The tests are quite simple, read some text and then answer questions based on that text by saying if it's true, false or you can't say. Really are not that hard and you have plenty of time to read everything and answer all the questions.
Can't remember if Credit Suisse's tests are SHL or Kenexa but it's one of the two. If you want to practice just google practice shl verbal tests. In terms of weighting, it's simple, if you pass a certain mark then you will be considered for the next stage. If you don't pass that mark your application will be rejected.