I’m not an expert at all, but I think mindful meditation kind of goes like this:

Decide on a phrase that you can repeat in your head.

Sit down somewhere, repeat phrase and focus on either the phrase or your breathing.

Every time your attention strays from breathing or mantra/phrase, bring your attention back to it.

Posture not ideal

Alternative Ways to Meditate
In the gym –
During the cardio/warm up – focus on any music that’s playing, don’t let your mind wander (or eyes), don’t think about or look at how long is left.  Focus on the music, 1 song at a time, try not to think about anything else.

When you’re doing weights.  Focus on the set your doing, a rep at a time. Don’t think of the exercises you’re doing after the current set.  Try to focus completely on each exercise, and try not to think about what’s going on ‘outside’ the gym (i.e. in work etc.)
Eating –
Can’t really do this if you are with someone else, but if you are own your own –
Be mindful and appreciate the food before you eat it, think of where it came from, the labour, the logistics etc.
Turn off the TV and any other distractions.
Focus on the food, try not to think of anything else, don’t think of things happening before or after your meal, just think about and savour the food (or drink)

Sod off Ted, I’m trying to meditate

In Work
If you work on a computer, got a coin, and cover the time up on your monitor.
Try not to think of what you are doing when you get home etc. Try and immerse yourself if your work if at all possible and again, if possible, enjoy it.
The main thing to try and do is not to think about your next break, or when you finish!

In the car
More mindfulness than meditation but…stop rushing to get to the endpoint of your journey, and enjoy the ride. You’ll get there, when you get there. You miss out on so many sensations, by living in the future.
Focus on the road though, always do that!

Benefits of Meditation
Improved focus

Decreased Stress – if you can live in the moment, you don’t worry about the future, or linger on the past

Enjoyment of menial tasks

“As it is, we are merely bolting our lives—gulping down undigested experiences as fast as we can stuff them in—because awareness of our own existence is so superficial and so narrow that nothing seems to us more boring than simple being.  If I ask you what you did, saw, heard, smelled, touched and tasted yesterday, I am likely to get nothing more than the thin, sketchy outline of the few things that you noticed, and of those only what you thought worth remembering. Is it surprising that an existence so experienced seems so empty and bare that its hunger for an infinite future is insatiable? But suppose you could answer, “It would take me forever to tell you, and I am much too interested in what’s happening now.” How is it possible that a being with such sensitive jewels as the eyes, such enchanted musical instruments as the ears, and such a fabulous arabesque of nerves as the brain can experience itself as anything less than a god? And, when you consider that this incalculably subtle organism is inseparable from the still more marvelous patterns of its environment—from the minutest electrical designs to the whole company of the galaxies—how is it conceivable that this incarnation of all eternity can be bored with being?”

~ Alan Watts, The Book: On the Taboo Against Knowing Who You Are