So often, people ask me specific questions about their own training, and just as often I find myself giving the same generic answers. The reason for this, I find, is that there is no one answer for how to train. Every athlete is different, and every week presents its own challenges. Circumstances change, goals change, and life sometimes "gets in the way" of our favorite rides.
It's important to be flexible when laying out a plan for yourself and to practice patience when executing it. You cannot always get the time in when & where you like - so be sure to compensate for that somewhere along the way. Be careful that you don't simply try to add miles/time to "make up" for a missed day. This is the shortest path to dreaded Over-Training!
There are many 10 and 12 week training plans out there (books and online), and these are a great way to start your training. You can learn a lot from these, but as I mentioned before - you must be careful to avoid over-training or even under-training. You must be flexible, make physical and mental assessments ("Is this really working for me?" "How do I feel today?" etc.), and do your research! Look around - not for the "best deals," but for the best sources.
One answer, of course, is to find a good coach who will know you. Someone with whom you can interact, give feedback, and who will create a fluid training plan, changing with you and motivating you along the way.
Ultimately however, it is you who is pedaling the bike and putting in the efforts. Hold yourself accountable. Give yourself a firm (but attainable) goal, keeping it in sight every day. Ride regularly. Get in the efforts, and above all else... remember to enjoy it!
Consistency is key.