I work for a mobile phone company over here in Australia... To help with credit, take Skullduggery advice get a pre-paid. If you take the number from the pre-paid over to the contract it shows the contract company your going for that you have a history with another mobile company.
Second, the company that your firstly going to may not take you as you don't have a credit history. What you can do is go to any phone company and apply... you may be rejected as you don't have a history, but after being rejected once, you've atlest opened a credit file. You would only be rejected on the base that no other credit file had been opened, it won't place a black make upon your name.
Third, look around for the best plan... what you might think is a good plan, say you get 20 free sms, may not be the best for you. It may have a high call rate, and charge by 30 seconds or even by the minute

... Look for something that is charging by the second. Also check with the included calls, the plan may state it is a $20/ 20 pounds a month with $20 / 20 pounds of calls... these are not free calls, the way it breaks down is that the $20 is the min. monthly fee. So if you only made say $10 worth of calls, you'll still need to pay $20, if you made $20 worth of calls you'll pay $20, and if you made $30 worth of calls you'll pay $30, you won't have to pay for the access for the phone + the calls you make... just what you go over with. If your going with a company that has free time calling within the same company, check with family and friends first to see if they to are with that network... nothings worse than being on a network that has free calls and nobody to call...

Also look at the handsets... there may be a phone that you want, but just be careful, the plan that it may come with could be quite high. Make sure you have a look at a working model aswell... you don't want to be on your way home and find that the phone just plain sucks...
I hope this helps...
