Here are some of the most common reasons for embarking on a PhD:

• I have a diagnosable mental illness.
• I cant get a job.
• I cant face the real world.
• I think it would be cool to have Dr before my name on my credit cards.
• I seek to further my knowledge and contribute to the advancement of science in this, my chosen field.
• I'm too ugly to be a model or an actor or a prostitute.
• I am impressed by the example set by my television role model, and wish to follow in his/her/its footsteps.
• Smart chicks are hot.
• PhD? I was just looking to put my application for the lab tech job, so that I can have a salary and job security and can still wear the funky white coat.

So, if you still want to do a PhD this is a good start:

• Obtaining That Elusive PhD
• Stuff most students never ask about grad school
• The Successful Grad Student
• Motivation
• Choosing a topic
• Managing your supervisor
• The Lord of the Rings: an allegory of the PhD?
• How is the PhD life... (it is also a motivation) 

Source: http://www.nigels.com (access date 22-Jun-2005)