A sample picture from my first "senior photo" shoot. Not saying this is a good shot -- I'm by no means even close to having enough experience shooting (let alone posing) portraits to be "good", but you've got to start somewhere.
Taken with the 10D, ST-E2 on-camera, 550EX firing into a Photek Softlighter II umbrella to camera left, another 550EX (ratioed down, probably too much) to camera right, also firing into a Photek Softlighter II. A (borrowed) 420EX was low and behind Ryan, to illuminate the backdrop. All 3 flashes were triggered wirelessly by the ST-E2.