One of the fundamental steps in good time management involves planning enough time to plan your time. Not clear? Let me spell it out: at the start of the school year you should look at your calendar-or-diary and write down when you are going to do your time management.
You should have regular (TM4T recommends weekly) planning sessions in your plan. This is not lesson planning. It means looking at your to-do list and your plan and deciding when things get done. You should also build in daily review sessions, looking at what is planned for that day, and modifying the plan if needed.
It isn't enough to make a mental commitment, along the lines of 'I'll do my weekly planning on Sunday evening, then every day after class, I'll do my daily review sessions'. The key to success is in using a written-down plan of what you're going to do. When you open up your diary (or calendar, or yearly plan) you should see your commitments staring back at you, with a specific time and a specific place: "Sunday 19:30 Weekly Planning in spare bedroom" and "15:45 Daily planning review in Room 3" every day Monday to Friday. These should be written down for every week in the school year, right at the start of the year (obviously this is a lot easier if you have an electronic diary).
When you are doing your regular planning, you should routinely break large projects into smaller tasks, and decide when to do those smaller tasks. 'When' means a specific time for the early tasks; and a period of time (for example a week) for the later ones.
You should routinely estimate tasks with precision, even if your estimate is inaccurate. In this context 'Precision' means an exact time, for example 3.5 minutes. 'Accuracy' describes the correctness of your estimate (for example the task may actually take 4.1 minutes). You should also routinely allow some contingency in your planning (10% is reasonable). Have some contingency time ear-marked for any overflow tasks