Besides using simple blocks, you can insert Things that other people have built into your Place. Use the Insert... menu in the game to browse.

Action Primary Alternate
Move Avatar Arrow keys ASDW keys
Move Avatar (no tool selected) Click location with green disk
Jump Space Bar
Look up/down/left/right Right-click and drag mouse
Look side to side Move mouse to the far right or far left
Zoom in/out and up/down Mouse wheel I (in) and O (out) keys
Change Tool / Toggle tool on off Number keys 1, 2, 3, ... Click on the tool
Drop Tool Backspace key
Drop Hat Equal (=) key
Regenerate dead or stuck avatar Avatar regenerates automatically Exit and then return to the Place
First Person Mode Zoom all the way in