Hair Extensions Explained

Hair extensions clips (strips and bits):

The most practical and most sustainable in my opinion! These are long strips of varying lengths. These clips are attached to the hairline.
The Negative - You need to apply them and remove them daily.
The Positive - You can re use them and change them up to suit your style or outfit for the day. Hair extension clips can last several months, even a year or two all depending on the quality and care that you give them.

Extensions glued to your hair (fushion):

Get these done at the hairdresser, it lasts 2-3 months in all. It's a bit more expensive than extensions that clip on, but the effect is super nice.
The Negative - After a month, some little bits start to fall off and you need to apply more glue. When it comes time to remove the glue from your head there is a lot of damage done to your natural hair from the roots.
The Positive - You don't need to worry about applying them daily as they are attached to your head permanently. The effect is supernatural.

Extensions woven into her head (weave):

A technique that I know a little less about. This method consists of extension bands like those with the clip, except that they are sewn into your hair on french braids.
The Negative -If extensions are very long and heavy it can put pressure on your hair and pull it out. Extensive use of this method over a long time can cause thinning of your own hair.
The Positive - Again, you are not obliged to remove them and place them every day, it is about 1 to 2 months well sewn into your head. And finally, each tape is reusable for sewing again later in your head, so it is far cheaper than those that are glued on!

Pictures of hair extensions gone wrong: (not emo or scene but you get the idea)
Britney Spears bad hair extension day:

Paris Hilton bad hair extension day: