Serpentines are a natural way to get your horse to naturally give to the bit, achieve a better trot, get that head down, and get your horse bending into the direction of any circle you wish to go. Even if you have a head tosser, a horse that takes off into a speedy trot, a stiff horse, or one that holds it's head real high, serpentines will correct those issues if done correctly. You should start seeing amazing results within a week but isn't going to get perfected for at least two weeks or more. Giving the release at the right time is critical in getting your horse to understand what you want. In most cases the horse will seem to get worse in the first 15 minutes. Keep being persistent as your horse is trying to figure out what you are asking.

SERPENTINES
Start at a stop. Grab the rein about where the horse's neck is and bring the right rein in towards your hip gradually until your horse gives. Make sure your left rein is completely slack. What I mean by "giving" is that if the horse turns his head into you then release the rein. Even if the horse just gives you an eye...release the rein. Praise. If the horse starts to throw it's head up or/and starts moving his feet you keep that rein in until the horse settles his feet(usually comes first) and gives an effort to give. Do not let go of that rein or let up until this happens or can send the wrong signal to your horse. You just taught your horse the beginning steps of giving to the bit and to bend. So, you work on this same side for awhile. Only ask for a little more give when he starts understanding what you want and becomes softer and more willing. Pretty soon you should be able to bring his nose to your foot. Once that is fluent and you bring the rein in and he gives fully(nose to your foot) then work on the other side. Make sure you praise with every effort. Once you are able to move his head from one foot to another in fluid movements then proceed to the walk.
Here, you are asking your horse to go right...then left....then right....then left. You might encounter the horse going stiff and start head tossing again. You just keep that rein tight until the horse gives slightly and makes an effort (whether you need to continue going in that same direction that's fine)then release and ask for the other direction. So, say your going right and you bring the nose in and you release the pressure and then the horse wants to go straight....bring the nose back in...release...back in.....release...and so forth until the horse is bending in the circle all on his own with a slack rein. Then ask for the opposite direction. Do the same thing in the opposite direction. Bring the nose in...release...bring nose in....release...so forth. Then move onto the "go right...go left...go right...go left" once your horse is giving freely in both directions. Once your horse is giving freely at the walk in both directions then call it a day. The next day start completely over back to square one. Once the horse is giving freely(this shouldn't take as long as the first day) in both directions at the walk then start at the trot.

Now....the trot. Usually the horse will start out very fast and very rough and when you are asking to bring the nose in they have a tendency to want to either walk or stop. Keep cueing for the trot. Once they realize they have to keep trotting then they slow way down into a "sitting" trot pace. Do the exact same thing at the trot that you did at the walk.
Do this everyday. You will see that the horse lowers his head, no more head tossing, trots very nicely, and most important....gives to the bit. Feel free to email me if you are needing further help with these serpentines.