The answer to this will change over time. At first you will want to make sure that you do it at least once per day, and at the same time each day.
One thing that must be emphasized here and now, however, is that you must never allow anything to interrupt the consistency of your meditations.
For example, you may lead a very busy life and look at the clock only to realize that the hour you have given to meditation has come and gone, and yet you are still at work or doing something else. This is the moment to give up the other tasks you had planned for the post-meditation period and to instead do the meditation!
Yes, you may need to forgo a meal, a workout, a meeting with friends, or that hour of TV, but it is essential that you do so. This is because strong meditative skills take many months to develop, but can be seriously damaged by a few days of absence. Go ahead and sacrifice an hour of sleep or a jog in the park because the energy you devote to meditating will be far more rewarding.
As you go deeper into meditation, however, you may find yourself doing some meditative exercises a few times each day. The ultimate goal is to be in a state of witnessing 24 hours per day, but that comes after long practice. When I first started a meditation practice in my early 20's one of my teachers asked me how often I was practicing. Proudly I told him about two and a half hours every day thinking he would be happy with my dedication. He shook his head and said why not six hours a day, why not twelve? This was an enlightening moment for me seeing that it was more about how you lived through the day and not just the short period of time during a focused practice.
How long should I meditate?
We just discovered that there may be no “best” time of day to meditate, and there is also no “ideal” length of time to spend in meditation either.
What is true is that most people just starting to meditate will find that ten to fifteen minutes is the longest period of time that they can focus without “forcing” the issue. As they become more experienced and learn what they need to gain clarity and awareness, they can easily extend that amount of time.
Additionally, some people prefer to do their meditation like they do their daily exercise – in segments.
So, you may find that 30 minutes in the morning and 30 minutes in the evening are ideal for your needs.
Generally, like so many other facets of meditation, it is going to be up to you as the meditator to determine the most appropriate amount of time to owe to your practice.