Target market is of course correct as suggested here by others, but other considerations are of course business acumen/skill set and amount of money you have to invest.
Choosing a data centre is not an easy task, but the UK would always be the best bet when starting out, then look at branching into other countries later.
Organic growth is the key thing, pay yourself enough to earn a living, but always invest back into the data centre whenever you make a big sale/or one big enough to do both.
Try not to pay yourself too much too quickly, as lack of investment in I.T. i.e. servers, more disk space, bandwidth etc.. will come back and bite you if you were to face technical problems later.
Keep the balance right between profit and investment, approach growth at a steady pace and keep your customers happy is the best starting point.