I read and still have both books mentioned The Body Language of Horses by Bonnie Ledbetter and Horses Talk It Pays to Listen by Parker. I still pull them out to read over again both are good introductory books on this subject. They are what got me started on using pre-race inspection as one part of my overall handicapping. In addition to my uncle "breaking me in" when he was working as a groom for Rokeby and Greentree in the late 70's and early 80's.
I Haven't heard of the seminar or tape by Tkach so if anyone has more info where I can get these please let me know.
Here are some (not all) general guidelines of what I look for in the Paddock.
Some Positives and contrasting negative body language:
-A dappled coat, which I'll describe as an exagerated positive indicator of a horses overall physical and mental health better than just a shiny coat. I describe it as looking like rings ratiating from within a horses skin along with a gleeming coat.
-Deliberate firm steps when walking or prancing, I want to see a horse firmly place each hoof down on the ground placing weight on all fours. You can often hear these deliberate firm steps as they walk or prance. To me this says the horse is sound. By contrast many horses especially when prancing appear to hardly be placing their body weight onto their feet as they move that's not to say horses that move softly are unsound as each horse is an individual.
-When a horse is standing still I want to see good erect confirmation, straight legs with toes pointed forward instead of turned slightly in or out. I love to see a horse stomping the ground a few times during saddling or when in the stall. They will usually do this with the front feet and to me this is the horse saying "lets get on with it".
-Another "lets get on with it" sign is when I see a horse nudging/pushing the groom in the paddock with their head. It looks like the horse is pushing on the groom to get going. The same behaviour I also like to see during the post parade the horse nudging, pushing along the lead pony saying I want to race today. By contrast you can sometimes see horses almost hiding beside the groom or trying to drape his neck over a lead pony for comfort or reassurance.
-The typical bowed neck with alert ears and eyes. I've seen many horses that do not bow their necks win many many races again they are individuals however a bowed neck goes along with the nudging and pushing foward of the groom and lead pony. I want to see an alert horse with ears straight up paying attention to the goings on with ears turning to hear the sounds of people and other horses.
-A demonstration of dominance over the other horses when walking past each other in the paddock. Horses are pack animals with a definate hierarchy. Two Horses walking past each other one with neck bowed looking forward with intense eyes and ears erect another almost shying away with the head dropping looking at but not looking directly at the other horse. Which would you want to have money on?
Some negatives:
-A horse barely lifting the feet or shuffling or sliding the feet when walking. If a horse moves like that in the paddock how well will they move on the track?
-A horse whinning. Many young horse will do this in the paddock. To me this says "I don't want to be here I want to go back to my barn, I want my mommy". This is often accompanied with other eratic behaviour like rearing up or signs of fear like seeing the whites of the eyes. The horse is scared and they do demonstrate it. This kind of a horse can settle down and run well the key is if the erratic behaviour continues to the post.
There's lots more to this topic and I can go on but I have to do some work now.

I will say that there is a caveat I have to face up to and that's because I grew up in Queens going to the races at Belmont and Aqueduct and now live in Saratoga county wagering mostly on the NY circuit. Many classy horses at the top tracks will demonstrate many positive signs especially in the graded stakes races, so you often can't eliminate many of the horses based on body language. At the lesser tracks I believe paddock and post parade inspection can be very useful and a powerful tool. I really have got to get over to the Finger Lakes more often
Phil Mandl