Get there with enough time to try and relax, and so that you don't feel rushed. Try not to spend too long on any one question, I found it easier to go onto the next question rather than getting bogged down, then came back to it at the end of the section. Good luck!
It's a fairly simple test to be honest. As long as you can count, read and have some common sense you'll do alright.
When I did it there was about ten of us. At the end the PO said he'd let us know one at a time how we get on and asked the first lad to join him in another room. After a few minutes he came in to the rest of us to say we'd passed. Even the girl with bright blue skinny jeans and orange hair passed.
I passed mine in in the summer of 1975, as mentioned before numeracy, English, and funny little mechanical problems. Joined up about six months later and stayed in as long as I could. Best job ever, finishing as a CPO Marine Engineering Artificer - now called CPOET(ME) I think!