I am thinking of moving over from the UK. First few months to try the place out but when do I need to legalize my position there (resident etc) and how do I go about it. Or do I need to do it before arriving?
When you arrive will be given a 3 month tourist visa. Don't worry about overstaying. You will only have to pay a small fine if you do deceide to leave. You can get your residency later.
You should apply for your residency when and if you decide to stay in the country to work. Applications for residency may be filed while in the country with a tourist card or visa.