As in any endeavor, setting some specific goals will help you achieve success at a more measured rate. Set your goals based on your level of writing expertise, the areas where you know you need help (such as grammar, plotting, research, etc.), on the type of writing that interests you, and whatever other factors come into play. For example, you may want to set goals in a number of specific areas, such as: hours of creative writing per day/week/month; time reading/analyzing target markets; time researching in the library or on the Internet; time sending out submissions; time reading how-to materials; etc. None of us have time to do everything we would like, so concentrate on those areas that are most important to where you are right now. Do not shortchange yourself in the writing and marketing areas if you want to succeed. The length of time set for each task is not as important as actually following through on it. You will be surprised how much you can accomplish in even 10-30 minutes a day of consistent writing time.
You may find it helpful to write your goals in a journal or on a wall chart, and then track the time actually spent in each area.