Get a sto-fen.
Use it.
Use M mode.
Select aperture & ISO (I suggest one stop down from widest aperture, if you have an f2.8 lens set it to f4, if you have an f4 lens set it to f5.6)
set ISO to 400 to help keep the exposure time fairly short.
Meter for the room at -1 or -2EV.
Go for it.
If you want to try bouncing be wary of colour casts from the surfaces you are bouncing off of.
If you can get some colour correction gel for the flash then get some, use Daylight to Colour Temperature Orange (hint get a free swatch book from Lee filters, the cinematographer one is the way to go) and set the cam to tungsten white balance (wee light bulb)
Good luck