Weight-painting hair particles I'm sure there's something simple I'm missing here. I'm new to Blender and I am following a short tutorial on Youtube regarding vertex groups and hair particles. (https://www.youtube.com/watch?v=EqRgaHMgf9g)

I follow the tutorial exactly, starting with a simple UV Sphere, giving it a color (Cycles Render is selected), creating vertex group that includes all of the vertices on the sphere, and assigning a weight of zero.

My problem arises here: he goes into the particle system settings and adds the vertex group to the Density control in the particle system's Vertex Group(2:03), and no hair particles show on the object. When I complete the same steps, the particles never go away. My vertex group has a weight of zero, and this is confirmed in weight paint mode, as the entire object is blue, but the particle system seems unaffected by the added vertex group. What am I doing wrong?
Your problem may lie in the fact that you used Cycles render while he tutorial is in, Blender render. This changes the UI and settings. Here is a video link by: Blender Guru, That hopefully may help you. https://www.youtube.com/watch?v=4_niVFliJ0E
You can change render engines after you have done the hair and it will keep what you have done.