What does a player do to get strong? This involves both physiology, choices, and attentional focus.
A good idea is to try to determine where your weaknesses are, so that when studying is performed, it is effective. That being said, study of any material related to Go or chess will have immediate and long term effects.
Length of time of study: Each person has their own attentional focus style which is affected by environmental and internal factors. These factors will influence the effectiveness of the time spent. Remember that understanding how things "feel" during study will also affect efficiency. At some point in studying there will be a diminishing return because of fatigue or cerebral overload, and it is at this point that time away from the material should allow the brain to "decompress" or start to consolidate the material. Do not study other material of a similar sort that may compete with the material just reviewed as there may be competition in the brain for the new material.
Self Talk during study: When studying chess/Go problems/games it is important to consciously focus on different things during studying such as strengths/weaknesses/opportunities/threats as well as positional/tactical and short and long term considerations affecting the overall plan. These attributions that are made consciously will give meaning to the material being studied and also train the unconscious mind as well. Initially it is said that during new behaviors/material there may be chemical changes at the synapse and with repeated application there is solidification through permanent neural wiring changes. By taking the small steps by consciously going through every move and placing meaning on it consciously, the neural matrix available for move determination for example during a game will continue to grow. It is very important to not rush through each move, take your time to get things right the first time. By taking the time to evaluate each move correctly during your study not only will the studying fit you better it will reward you with newfound strength.
What to study: Hard tactical/checkmate problems should be performed first when you are not tired. If your speed/accuracy starts to decrease after 5-10 problems, then is a good time to review games. Find a player that you like, download their pgn files, and go through their games. Try to understand their thinking patterns of why they chose what they did, or what you would have done differently. I generally study the games of top women players because this challenges me to think differently and look at playing differently, as I am male and think somewhat differently than most women, of course this is open for interpretation as biological gender doesnt influence all attributes of thinking. Nonetheless I appreciate the beauty of the games that the top women players offer. I also appreciate the endless supply of material in the form of books and online material. This brings comfort in knowing that I can never exhaust the supply of study materials with a virtual online library!
So in studying, correct length of time of training, correct material and correct length of time after studying(say 1-2 hours) to allow for consolidation of new material will help to great lengths in getting stronger.