Obviously, to avoid straight flash, you gotta get the light off the camera. Sometimes this is easy. Leave it hot shoed to the camera, crank it up, and bounce it off the ceiling. Or the wall. Or swivel it 180 degrees and bounce it off the wall behind you.
Remember, it's always good to redirect the light. That can be very easy, or it can be a bear. With wireless TTL flashes, just keep a master flash on the camera and a remote flash in your pocket or camera bag. Pull that puppy out and start moving it around. Remember it's a game of inches. Even getting the light source out there at the end of the reach of your arm makes the light better.
Unfortunately, I'm not Mr. Fantastic and I can't stretch my arm over a highway. Getting the light off the camera on this shot included a 30' boom, a heavy movie-style stand, a couple hundred pounds of sand bags, a whole bunch of rope, three assistants, my pickup truck, a hand-held camera flying along a couple inches off the pavement, a lead car to warn off oncoming traffic, some very illegal highway maneuvers, and a high-speed vehicle duet that was right out of The Road Warrior.
All to get that cheek shadow on the camera side of his face. Looks like he's drivin' west, headin' into the sun.
Straight flash? Highway heats up, the bike chrome gets nuked, and a lot of the tough-guy-on-the-chopper feel goes away. Straight flash makes him small, something Mr. Welbourn, an offensive lineman in the NFL, is very definitely not.
(Excerpted from: The Moment It Clicks. Photography secrets from one of the world's top shooters. By Joe McNally, Copyright 2008 Used with permission of Pearson Education, Inc. and New Riders.)