1. Go to http://www.amazon.co.jp

2. Click "Your Account" button (top right)

3. Click "Click here" next to "Would you like to see this page in English?" sentence (top left)

4. Scroll down, click "buy" on the "Redeem or buy gift certificate" sentence (bottom right)

5. Click the long yellow button

6. Type your email address and if you don't have Amazon Japan account choose "No, I'm a new customer" then click the yellow button

7. The sign up form:
name
name again
email
email again
birthday (optional)

password
password again

8. Complete the Gift Certificate form (it should be in English)
Amount has to be in Yen, so please use online exchange rate calculator such as: http://www.xe.com/ucc/

9. Insert your credit card information

10. Check the confirmation page :)