Training is simple to set-up and involves pushing sliders on the various aspects of each sessions up and down to set your session up.
The default schedule which outfield players start upon is aimed at being a balanced schedule and will generally maintain all attributes - you can increase the workload of this schedule, but you will tire players out more and increase the chances of them getting training injuries.
You could decide to divide your players into schedules based on areas of their game that they are lacking on. You may decide to have 3 or 4 basic schedules focusing on improving fitness, ball control, etc. Alternatively you could create a custom schedule for each player as no two players are alike and each may require individual training.
If the end results you require from training are for fitter, better players then you'll need to get your coaching set-up right. Look at their attributes to determine their proficiency in each of the training areas and allocate them to routines that suit their skills. Clearly, if you are at a smaller club, you may not have the resources to fund a range of coaches, but regardless of your current club, it pays to understand how coaches work and how their ability to improve your players can be hampered or improved.
The ideal setup is to have 5 star ratings in each training category (see Training, Coaches accessed via the left-hand panel in your Squad menu). A very good coach assigned to just the one category will give you 5 stars if his coaching rating is high in that particular area. The more categories that he is assigned to, the lower his coaching rating will be for each category. For example if you have a coach with a rating of 20 for attacking coaching, you will get a 5 star rating for Attacking if he is assigned only to this category. If you assign him to 2 categories you may only get a 4 star rating on both. If you assign him to all of the categories, you may only get 1 or 2 stars.

You also need to make sure the workload isn't too high otherwise players will suffer from not getting enough attention.
It takes around 2 months generally for most players to receive the full effects from starting a balanced, normal training regime after a period of inactivity.
Obviously, if after someone has reached the peak on their current training regime you then alter it so that it concentrates more on one area and less on another he will gain points in the more vigorously trained area but also be liable to lose points from the now lesser trained area.
Heavily training players can make it harder for them to stay fully fit and therefore ready for matches. If you have a key player who is struggling to cope with the repeated demands of matches during a season consider lowering his training regime slightly. You might find he loses his edge slightly because he's training less, but that's better than him not being fully fit.
You can find the option for retraining a player for a specific position in the 'training' section of a player's profile.
Players tend to be more likely to progress with position training if they are young than when they are old. Exceptions to this do exist, notably for hard-working players moving into more defensive positions as they get older, however these are quite rare.
The likelihood of a player retraining for a position is dependant upon his preferences and abilities; a defender with a 1 finishing and no interest in attacking is thus unlikely to be particularly motivated to retrain as a striker whereas another fellow defender with 8 finishing and 8 off the ball will probably be very interested in retraining in that position.
When retraining a player, if successful, you will find he moves through a series of stages towards being 'Accomplished' in this position. A player can never be trained into being a 'Natural' in a position, it's something you're either born to be or not.
The various stages of development for a position include:
- Accomplished
- Competent
- Un-convincing
- Awkward
- Ineffectual