Take a piece of foam core, or matt board and place it next to your light source (continuous light). Hold the board either to the right or left of your light. You will be able to see where the light is falling on your subject (or where it is blocked) You can also use two boards and place one on each side. BHphoto has flag kits that you can buy, but I found the matt board works just as good. You will need someone to hold it for you unless you buy a flag stand or are close enough to your light source to do it yourself. You can also place the matt board at the bottom and angle up or at the top and angle down depending on your needs.

You can also use reflectors and different colors for different effects, i.e., gold, silver, etc.