What the heck is guide mode when it's at home?
When should i stop using the auto mode and start using the guide mode.
I would personally use either shutter priority or aperture priority in situations where you really don't want to loose a shot and use manual for everything that you have the facility to shoot on a regular basis.
You will get a greater sense of satisfaction knowing that you nailed the shot how you wanted it rather than how the camera thinks it should look.
Shoot, shoot, shoot and read on these boards and post pictures for feedback.