Time management is about having conscious control over the amount of time dedicated to your various tasks, with weighting given to priority and return on your efforts.
The goal of time management is planning so that your efforts yield greater outcome. Among the easiest mistakes to make is to spend too much time on tasks that have insufficient priority. Many professionals have made careers out of teaching effective time management, and this is a subject which is important enough to consider getting getting some formalized training, or at least picking up a book or listening to an audio-book.
The 'Blog-Post' version of how to be effective however is pretty simple, and it comes down to two steps; Prioritize and Focus.
1. Prioritize: Make sure that you're identifying the tasks that are important, that need to get done, and that will have the most value at the end of the day, the week and the month. Far too many small business owners spend their time doing things they could pay someone else to do, while they neglect to do things that would keep their business growing, and that they can't delegate out.
2. Focus: So much time is lost to changing gears in between tasks, and to handling little pieces of larger projects or issues but not handling the whole, necessitating returning to the task again. This is not to mention the interruptions and distractions of business and life. Organize your time as if you were an administrative assistant (which you are) working for an executive (also you). Block out time to accomplish specific tasks, and then do those things at those times. Include goals that are the "Must Accomplish" tasks. Once you've laid out a schedule and priorities, stick to it.
Plan your time ahead of time. Prioritize and Focus. Keep yourself out of the weeds. Manage yourself more effectively by managing your time.