There are several ways to find an Internship and I will discuss all of them. You can either spend a lot of time on the phone cold calling companies and emailing them your CV, ask a friend who is in the sector of your choosing to pass your CV around to the management, advertize yourself on free advertizing websites (such as Gumtree or Craigslist) or you can go to a Work Placement organizer who charge a small fee to place candidates in the sectors of their choice.
Cold calling: This does take a lot of time. But companies will see you in a very favourable light and think you have lots of initiative if you spend time calling the companies you want to work with as a volunteer. If you can email your CV to as many companies as you can, they can always pass your CV on to other colleagues in the business/ similar companies they are in contact with. The downside to this method of cold calling, is that it can take ages to get anywhere and you may have to call between 50- 100 before any give you any consideration. But on the up- side- it will pay off when you get the internship, and later on job of your dreams
Friend in the business: This can be useful if you have family friends (parents friends) who have established their careers and know a lot of people.
Work Placement Organizers: These can be really useful. You normally pay a small fee and the work placement organizer will arrange for you to get a company of your choice and to get an internship that will really suit you.