Make a new document, about 400x400 pixels is a good size to start with. I usually try to work at twice the intended resolution, in case resizing is needed. In this way, your images will be smoother when you resize them.
Now, using the Eliptical Marquee Tool, hold down shift and make a big circle. Drag from the upper left to lower right, so that the whole thing fits on your document.
Step
Three
Pick out two different colors to use for the
shading of the sphere. You've got to use similar colors, but in different
shades. For mine, I'm partial to orange, so I mixed a very light
orange, coupled with a dark orange. Make the lighter color your foreground,
and the darker one your background. The colors I used are below,
if you want to try those first.
#FFDEBA (light orange)
#E64B00 (dark orange)
Step
Four
Take your Gradient Tool and hold down shift, then
drag from the upper right of the elipse to the bottom left. Make sure
that the tool is constrained at 45°, or else it won't look right.
You want to try and get as smooth a gradient as possible.
If you made a mistake the first time, just press CTRL-Z and try it again :)
Behold, the Gradient Tool!
Since we're pretty much done, you can add whatever you like to the sphere to make it more realistic. Maybe some lighting effects or a drop shadow, it's up to you! Some finished examples of mine are on your right.
