I agree with onepage on learning to shoot in manual to take control on the lighting on the scene. Also learn your different metering modes such as evaluative, spot, and center-weight etc.
Shooting in Av (aperture priority) and Tv (time value) modes are great too to test the waters before jumping into full manual.
Also learn to "see" the scene and correct Ev (Exposure compensation) to match what you see.
Just a side note: the 1000D is an excellent beginner camera. The image quality is still very nice, just make sure to try and keep the ISO 800 and under.