Select (Spacebar)
Paint Bucket
Rectangle
Circle
Move
Rotate (Q)
Scale
Tape Measure
Orbit
Zoom
Eraser
Line
Arc
Push/Pull
Offset
Zoom Extends (Shift-Z)
Here are some tips to get you started with drawing in Sketchup
TIP 1: SETUP
Go to MODEL INFO and set up the most appropriate UNITS OF MEASUREMENT and PRECISION. You can also do this by choosing an appropriate TEMPLATE if you're asked
TIP 2: ALWAYS DRAW NEAR THE "ORIGIN"
Draw just to the top left of where the axes meet
Try drawing what the object should look like from the top - use the proper DIMENSIONS
Don't be afraid to undo and try again if things are out of scale