I’m new to lighting photos, but have been successfull with the following.
I used an f8 (if I remember correctly) to have an reasonable focus range and the Tv on BULB with a cable shutter remote. you can experiment with 10 – 30sec. Then with regards to focusing I used manual and turn the focusdail to infinity and then I turned the focusdail just a tad back so that the lighting which is normaly on the horison will fall in the focusrange.
I also used iso400 & 800.
I used a wide lens (17-85mm ) and looked where most of the lighting was pointed my camera in the general direction and released the shutter. Just look on your LCD and adjust accordingly. You quickly notice that the exposure was too short if the LCD is too dark.
By the way out of about 25 photos I like 6. so don’t give up.