Most meditation instructors I know tell their students to sit for 10 minutes a day. I tell my students to do that if they can, but if they can't, just commit to one single Mindful breath a day (see: Just One Breath a Day). A friend jokingly called it "Mindfulness Lite". I teased him back by saying, "No, it's much worse, it's Mindfulness UltraLight".
In practicing meditation, one often comes across interesting surprises. My biggest surprise in practicing Shamatha (Calm Abiding), a practice leading to profound concentration, is the insight that relaxation forms the foundation of Shamatha. When the mind is relaxed, it becomes more calm and stable. These qualities deepen Shamatha, which in turn strengthens relaxation, thus forming a virtuous cycle. Paradoxically, deep concentration is built upon relaxation.
A similar mechanism seems to work in the practice of Mindfulness. I found lightness to be highly conducive to Mindfulness. Lightness gives rise to ease of mind. When the mind is at ease, it becomes more open, perceptive and non-judgmental. These qualities deepen Mindfulness, which in turn strengthens lightness and ease, thus forming a virtuous cycle of deepening Mindfulness.
That is why I like my Mindfulness served light. Mindfulness is best when it is strong, and paradoxically, light and easy may be the best path towards strong. Yes, there is a degree of cosmic humor here.
This insight suggests that a really good way to practice Mindfulness is during experiences of joy, especially the type of joy with a gentle quality that doesn't overwhelm the senses. For example, when you are taking a nice walk, holding hands with a loved one, enjoying a good meal, carrying a sleeping baby, or sitting with your child while she is reading a good book; these are great opportunities to practice Mindfulness by bringing full moment-to-moment attention to the joyful experience, to the mind and to the body. I call it "Joyful Mindfulness".
The first effect of bringing Mindfulness to joyful experiences is they become even more enjoyable, simply because you are more present to enjoy them. Extra enjoyment at no additional cost (really exciting for the bargain-hunter in me). More importantly, I found this Mindfulness gain to be generalizable. What that means is if you practice and strengthen Mindfulness during joyful experiences, that gain in Mindfulness infuses into other experiences as well, so you end up with stronger Mindfulness in neutral and unpleasant experiences too.
Joyful Mindfulness. Have fun on your way to Enlightenment. What a great deal!
Truth be told, I think you actually get much more bang for your buck doing formal sitting Mindfulness practice. Formal practice requires you to bring Mindfulness to your breath for a prolonged period. This is good because our attention naturally gravitates towards things that are very pleasant or very unpleasant, generally ignoring things that are neutral, so when you train yourself to bring Mindfulness to something as neutral as your breath, that Mindfulness gain is very generalizable, far more generalizable than the Mindfulness gained from joyful experiences. Pound for pound, you really can't beat sitting on a zafu. Unfortunately, formal practice requires lots of discipline, and discipline is a scarce resource, making formal practice hard to sustain. In contrast, Joyful Mindfulness offers much less punch but is far more sustainable. Plus it's fun, and nobody can argue with fun. I know I can't.
I think it is most optimal to do both formal meditation and Joyful Mindfulness everyday. By doing both, after a while, your formal meditation may get infused with a calm, blissful quality known in Sanskrit as sukha, and the stimulus-free experience of sitting meditation becomes joyful. Almost all seasoned meditators I know arrive at sukha at some point in their meditative careers, however, my own experience suggests that Joyful Mindfulness intensifies sukha in formal sitting. I theorize that practicing Joyful Mindfulness got my mind accustomed to ease, humor and lightness, thus allowing it to connect with sukha more readily during formal practice. That sukha then quietly infuses into daily life and makes daily experiences a bit more joyful, thereby increasing the frequency and intensity of joyful experiences that I can then use for Joyful Mindfulness practice. And thus, another happy virtuous cycle is formed. Joyful Mindfulness works great by itself, but becomes very powerful in combination with formal Mindfulness practice.
I think Joyful Mindfulness reaches its best when even doing nothing becomes a Mindfully joyful experience. Because of that, and because Joyful Mindfulness requires so little extra effort, I jokingly call it the "Lazy Way". I tell my friends I strive very hard to be lazy. Be not afraid of laziness; some are born lazy, some achieve laziness, and others have laziness thrust upon them.