
My Manual Training Method
So you want to manual train? Sure we all do! No we don't but for those few, proud and daring players the micro managing aspect of Starters Orders is very fulfilling. I have been manual training since the first incarnation of the game and have my own methods that I stick to. Still I always feel I could improve on it so if you see something I'm missing or have your own advice feel free to add it.

Here's a 5yo game starter I will use. I treat older horses training slightly different than 2yo's - I race them more often. Depending on the horse's training status indicator color - for the first race I look for a race either 21 (amber) days or 28 (red) days ahead. Finding one near to these dates is what I choose.
For a first race for an unknown quantity gamebred I try and find a Maiden race at the exact breeding indicator distance. If that can't be found I look for a race slightly shorter in distance. I prefer a horse running on late in a debut than a horse weakening in a longer race if I'm going to lose.
After a race is found I turn the training intensity to amber (mid) and skip ahead day by day with the 'skip today's racing' button until 14 days before the race. I then set the training intensity to red (heavy) and then skip to day before the race. I start this training regimen at 28 days or less before a race. Never longer than 28 days - you wear your horse out faster if you do.
On the day before the race I turn the intensity back down to amber because it makes sense to me that a horse shouldn't be on hard training the day of the race. I don't know for sure if hard training on the day of the race has any effect on the horse's performance but I did notice (I may be imagining this) that the frequency of "slightly agitated" and "totally worked up" seemed to increase when training is left on hard the day of the race. The day of the race your horse's readiness indicator should be at green (ready).
The drawback to training on mid the day of the race is your horse is more likely to drop down to amber readiness from green. This is where I have a gripe with the game - when you run a horse at amber level the chances are 50-50 the horse will pull up or break down despite the fact it was green just the day before and it is literally one day off of peak. The game AI obviously rolls the dice when you run a horse on amber to see if it breaks down. I would prefer (beg Mark) for something fairer like your horse not running to its full ability when it is so close to peak fitness.
Here goes his first start - for any first time starter (gamebred or homebred) I always let the jockey choose his own orders. You quickly get an idea of how your horse likes to run.

He ran okay but he is no beast.
Now to decide on the rest period after a race. This horse was barely affected by this race. I will give him my short period rest (14 days off). If his condition bar took a big hit I would've given him 21 days off and for the slow to recuperate horses even more time off.
On a side note to this - Handicapping a bajillion real life races over the years I have noticed most US trainers give their horses 14 days off after a race before they start the workout schedule again. Whenever you see a horse getting a workout less than 14 days after a race give that horse extra attention - it's most likely knocking down the barn doors to get back on the track. Conversely a workout more than 14 days after a race indicates a lot of times a tired or hurt horse.

Now after the horse has run once I stick to finding races 21 to 28 days after the rest period is up and sticking to the training schedule explained above. Exceptions of course being high value target races that come up very fast that test your horse and you as a - manual trainer.
*Some extra points*
I always train my horses on Stamina emphasis. This setting a lot of times gets your horse's stamina bar to rise more and your horse will get longer distances than its breeding indicator. Also your horse's disposition most times will increase to laid back which virtually eliminates the occurrences of agitation in the paddock on race day.
On rest days if your horse is lacking in special training categories (Agility and Starting) check a special training category to train in. Over time your horse will improve in these areas.