mod4 starts managing mode. mod4+shift is for moving stuff around (mod4+shift+2 moves the currently active window to desktop number 2. mod4+2 simply switches to desktop number 2.
mod4+j/k selects the next/previous window of the current desktop; the order is shown at the top with the taskbar-like thingy. mod4+shift+j/k moves the windows around on the current desktop.
mod4+space selects a different layout for the current desktop. A layout describes how windows are placed on the desktop. mod4+u jumps directly to the window which has set a highlight (or urgent) flag.
mod4+m takes a window out of the normal layout control and makes it fullscreen; pressing mod4+m again resets to "normal" behavior. mod4+shift+c is essentially the same as clicking the "x" in conventional window managers.
windows can be dragged to a new position with mod4+leftclick. Windows that have the floating flag set can be dragged to any position, normal windows will snap into their new place according to layout.
Usually windows do not overlap; exceptions are floating windows, maximized windows (mod4+m), and when in fullscreen layout.
Layouts can be configured, maybe even on the fly using lua. awesome does have a notification area that is compatible with the freedesktop.org specification which means gnome and kde tools can use it. I haven't found a taskbar thingy that is compatible with applets from gnome.
mod4+r starts a command prompt for launching whatever commands you want. I am certain you can define keyboard shortcuts for programs you use often.
That's all for now