Don't be nervous, take it as a game, that's what works for me. In the end it is fun, isn't it? Setting up your mind for the kind of task you are going to do is also good - just thinking of numbers and letters, cubes or symbols for a minute or two before you start.
However, personally, it helped me the most to hear the others turning the papers at Stage 1, as I thus knew I am ahead of most of them :-)
(I passed but I failed the subsequent online personality test, which in my opinion is much more tricky and IMHO much less objective than the other Stage 1 parts.)