First, as you create your training plan, plant a stake on the calendar for the weekend of your key race – the race at which you want to be 100% tapered and ready to go. And, no, you cannot be 100% ready for every race of your competitive season. Then, from that race date, count back to today and see how many weeks you have to prepare.
Now, it’s time to break those weeks into chunks of time. The generic approach is to schedule 3 hard weeks followed by 1 recovery week. What I’ve found is that with the proper balance between key training sessions and recovery, training cycles can be extended to 5- or 6-week durations. Sometimes as long as 8 weeks. What’s critical here is to plan those recovery week deliberately. Put them on your calendar and lock them in. If you don’t do this, you will almost assuredly just keep on training hard and create the risk of plowing headfirst into the dreaded over-training brick wall.
Once you’ve created your various training cycles, you then need to determine how you’re going to balance your hard, easy and long workouts. If you’re a single sport athletes, this is tricky but straightforward. If you’re a multi-sport athlete, the challenge grows by an order of magnitude because you are also having to balance the frequency with which you perform each sport. If you’re a triathlete, you can create a very balanced and realistic training plan on 9-10 workouts a week (3-4 per sport).
Lastly, it’s key to determine how you’re going to balance and execute the various intensities at which you can train – from recovery to tempo to LT to VO2max to sprints. All of these are important to ensure your engine is firing on all cylinders come race day. By determining how many weeks you have to prepare for your key race, breaking that time into however many training cycles make sense, determining the flow of weekly workouts and, finally, overlaying the intensities of the key workouts depending on how far away or close you are to your key race, you should be able to train more effectively and, thus, hit race day with greater confidence in your ability to perform.
What's important is to start with the most intensive intervals and gradually come down in intensity one wrung of the ladder at a time. Conventional coaching advice (still) proposes climbing up the intensity ladder rather than down it. Do what you will but the latter approach to the ladder will be less effective and, ultimately, put you in a position of being less prepared for your key event(s).
Training properly is part structure and part finesse. The structure part is easy, as long as you have the discipline to follow the plan. As I like to say, "Plan your work, then work your plan." The finesse is really where the value of a coach comes into play; it is the unique athlete who can self-coach with finesse. In any case, creating the structure is the first step, something every athlete should be able to do for himself/herself.