I recently had a call from an acquaintance who purchased a co-op apartment a couple years ago. This person's lifestyle had changed up a bit and he was thinking about converting his one bedroom apartment into a two bedroom by splitting the bedrooms. He had done careful planning and measuring and was able to arrange the rooms so that a window and closet would be available in each room. His question to me was: how would this affect the eventual sale price of his apartment?
The most general answer is that renovations generally affect sales prices positively, but it depends on the type of renovation and execution. Then, I ask another question. Once answered, the homeowner will have a better idea of what to do and how.
How long are you going to be living in this home?
Food for Thought: If you feel like you will be moving within the next 2-3 years or less and selling your home for any reason (need more space, plan to relocate, etc.), then any renovations you do should take into account the next owners of the space. For instance, if you divide your bedroom into two rooms, make sure that you frame the wall in a way that minimal damage is done to the underlying floor and walls. This way, the extra walls can be removed so that the next resident can choose his preferred layout.
Likewise, refrain from making statements that are too bold in kitchen and bathroom renovations. Choose neutral tile colors such as earth tones in the kitchen and clean colors such as blue or black and white in the bathroom. This will appeal to a wide range of future buyers (who won't feel like they need to gut the apartment) and will still give you a fresh new home that you can enjoy. If you feel the need for bold choices, express your style with paint colors and furniture, items that will be easy to change for the next homeowner.
If, however, you plan to live in your home for a fairly long time, feel free to make more customized renovations, choosing bold tile colors and building in customized fixtures. It is, after all, your home for the foreseeable future, and you should enjoy it to the utmost!