This post gives gives a lot of information on how mindfulness works in our minds. If you like to know how things work, read it. If you just like to know what works, I like this summary:
So practicing mindfulness is important, as you're more likely to then remember to do it.
The key to practicing mindfulness is just to practice focusing your attention onto a direct sense, and to do so often. It helps to use a rich stream of data. You can hold your attention to the feeling of your foot on the floor easier than the feeling of your little toe on the floor: there's more data to tap into. You can practice mindfulness while you are eating, walking, talking, doing just about anything, with the exception of drinking a beer in the sun, which works for only a limited time before your attention leaves to go and party (the neuroscience of all that will have to wait for another book.)
Building mindfulness doesn't mean you have to sit still and watch your breath. You can find a way that suits your lifestyle. My wife and I built a 10 second ritual into the evening meal with my kids, which involves just stopping and noticing three small breaths together before we eat. The added bonus is it makes a great dinner taste even better.
What ever practice you do develop, practice it. The more mindful you become, the better decisions you will make, and the more you will achieve your own goals, rather than other people's goals for you.