Here is a quick tutorial video I made about how to tie a karate belt.
http://www.youtube.com/watch?v=_uRQ2ESpMQo&list=HL1341420171&feature=mh_lolz
Here is some information about the belt system in our karate style/school. Remember, different karate schools/styles may have different belt systems.
White belt is the belt that you have when you first start. It symbolizes that you are a clean slate, ready to learn. Even before you get your gi you are a whitebelt. The sequence of underbelts (belts below blackbelt) in our system are as follows... white, yellow, orange, green, blue, purple, brown, and black.
When a blackbelt is a 6th degree blackbelt (blackbelt with 6 stripes) they can get a red/white belt. This indicates that they are a master of their style. When a blackbelt has a red/white belt, they are still a blackbelt. For example, Sensei Tammy is a 6th degree blackbelt with a red/white belt. She can choose which of her two belts to wear.
When a blackbelt is a 10th degree (blackbelt with 10 stripes) they are eligible to get a red belt. O Sensei the Grand Master of our style wears a red belt, but not every red belt is a Grand Master. There is only one Grand Master of our style at any given time.