PCR uses short pieces of DNA to initiate replication starting at a very precise region. You choose your primers based on DNA flanking what you wish to clone. A good video showing how PCR works is available from McGraw-Hill, as well as another here, although the Internet is full of great videos. PCR is a staple of laboratories, so you can find what you want fairly easily. Whatever you do, though, don't go to this site that advertizes thermocyclers! (If you clicked on that link anyway, I dare you to get the song out of your head).
Here's the question. Give it a try before looking at the solution video:
The solution is below.