I wish I had an underwater camera and someone to wield it. About a year ago I started studying the Total Immersion style of swimming and adapted much of it to my stroke. More recently I started reading Swim Smooth’s newsletter and studying their philosophy of how to swim freestyle. I’m 60 years old so I’m more interested in going long at a good steady pace. I do some sprints but although I did a 32 second 50 meters recently it puts too much pressure on my old shoulders so I think, in future, I’ll stay away from those short races. I warm up with 800 meters – at about 13 minutes which puts me in the top 5 or 10 for my age group depending on the year. I glide. Just a little bit. But that is where I would love to be videoed. I have kind of developed my own stroke that moves me along pretty quickly. (Probably closer to Total Immersion than Swim Smooth)
That said this is a pretty good article on the amount one should glide: http://www.feelforthewater.com/2012/03/overgliding-inefficiency-and.html
The Total Immersion style is pretty heavily promoted for Tri-athletes and I think works for us ‘older’ guys. But I would advise studying both and seeing what works for you.