1. Use some credit
It's a common misconception that because you've never had any credit commitments, your credit score will be good; that isn't necessarily the case as lenders like to see a track record of keeping up to date with your payments, so having a small credit card balance that you pay back every month can be a good thing. Paying things like utility bills and mobile phone contracts can also help.
2. Register to vote
Not being on the electoral roll at your current address can negatively impact your credit score, lenders use this for confirming names and addresses so the longer you're on the electoral roll, the better.
Register to vote here
3. Check your credit report
Sometimes there can be things marked on your credit file that might come as an unwelcome surprise to you, make sure you keep on top of your credit file by checking it regularly and disputing anything you don't agree with.
Having lots of credit checks on your file also impacts your credit score, so make sure you don't apply to lots of different lenders for credit products if you're thinking about a mortgage or other loan.
4. Breaking old financial ties
If you've had credit products with a partner or friend previously, this will show up on your credit file and potential lenders will see this and may consider that person's credit score as well; so be sure to be close down any historic credit arrangements that are no longer active.
Another note is to close down any accounts of yours where the balance is nil, if you had a credit card and then paid it off, the account will still be active so make sure you close it down with your provider, this is important because lenders assess not only your current credit commitments but also your ability to access to credit.
5. Explaining unusual circumstances
If you've fallen in to financial difficulties that have affected your credit score due to illness or redundancy, you can add a notice of correction to your file which potential lenders will be able to see and consider.