Having this information not only helps you document your training, it also gives you a solid foundation for presenting procedural and policy change suggestions to your superiors.
Record Keeping
Make sure that you store your records in a safe place. Some officers I know use filing boxes. Others have actual file cabinets in their homes where they store all sorts of important documents, including their training records. Whatever works for you is fine.
The same is true of how much information you maintain. It can be as simple as keeping copies of diplomas or records of attendance. Beyond that, you can get fancy and do things like scan the documents into a computer and make a copy on disc. That's a great idea if you have the means and the desire, but it's not necessary. I don't really have recommendations on how to store your records. My primary focus is on getting you to keep them. However, I do have some suggestions on what to keep.
Maintain a chronological list of your training. This list should include the date of attendance, title of the course, and the number of training hours. That last one is more important than some of you can imagine. When your judgment or professionalism is called into question, countering with the exact number of training programs and training hours that you have experienced can have great impact. Also, if you have specific expertise in fields like officer instruction, accident reconstruction, crisis negotiation, etc., then documenting your training can lend weight to your testimony as an expert witness.