Just how simply - and how inexpensively - can you shoot great headshot photos?  Very - if you plan it correctly from the start.
   Assume you have the key essentials - a good dSLR, a good lens, a good speedlite, and a good tripod.  If you don’t already have a great background, a piece of foamboard is under $3.00 at Wal-Mart; the basic white one works great for most skin complections and most clothes - while a similar blue foamboard from Office Depot is light blue on one side, dark blue on the other and is thus great for other clothes.  Then all you need to shoot great headshots is a remote and a good diffuser for the speedlite - if, that is, you don’t already have both.  And a simple infrared remote such as Canon’s RC-6 works great.  And all of the things you might not already have will be around for many other kinds of photos - again, at nil cost.
   A speedlite with an inexpensive diffuser - such as the under-$20 Sto-Fen Omni-Bounce - holds up putting out great light a lot longer than any ring light powered by two AAA batteries!  Put the diffuser on the speedlite - and bounce it off the white ceiling; it will be far better at avoiding shadows behind your subject than a ring light mounted on the lens or dSLR.  It will very rapidly cycle - and not change light output.
   As always, any subject who is male or transgendered needs to shave immediately before the session - or every whisker will show!  Hair also needs serious attention before shooting.  They need to be posed with their feet at somewhat of an angle to the camera, but with their face somewhat more towards the lens, to look thinner.  Experiment with posing them looking slightly up, slightly down, and directly into the lens.  This will avoid the “mug shot” look, too.
   Zoomed in rather tight to the face is best.  Expect to shoot dozens of poses - and pick the best from them.  
   Don’t forget to bill the client for the batteries you replace after each session!

   Shot with Canon 7D 24-70 f/2.8 lens, 430 speedlite, Sto-Fen Omni-Bounce, tripod, remote.