Much as the same before you will need to provide a reference. I strongly recommend using somebody who is an academic member of staff at the university you currently attend, ideally a class teacher. Generally, the more senior the position held by the referee the better, however it is appropriate to get someone that is representative of your abilities.
More often than not, the person asked to provide the reference may never have done so before, so its best to be prepared to offer guidance if requested. The reference should detail how you are as a student and highlight all of your strengths and why they would recommend you to study the new course.
You will need to supply another personal statement as previously done and it will have all of the same requirements as for other applicants.
I would recommend you include a paragraph or two about why you want to switch. 9 times out of 10 this will often be asked by the admissions office and passed onto the correct person separately, however it shows that you are making more of an effort – and you want to have the best possible chance!
It’s best to emphasise what you have gained from the previous year at your current university and how it will help make you succeed even further at the new one. If you’re applying for a particular university then I would strongly recommend writing about specifics of that course and why it interests you and try and tailor any previous experience to help your chances.