Meditation as a verb, means to think deeply on something, yet the true goal of meditation is to still the mind.
A common complaint I hear from those who try meditation for the first time, is that their mind just won't shuttup.
I think Eckhart Tolle said it well when he described how, at the beginning you're sitting there quieting the mind and a few minutes later you've decided that you're quite hungry and your mind is already half way down the road looking for a restuarant, but you haven't left your seat.
What I do when I meditate is to relax in a comfortable chair, close my eyes and become as much of an observer as possible. One of the easiest things to observe is ones breathing.
Whenever I find I have gone down some mental detour, I gently bring myself back into observer mode.
By continuing to do this, the mind quitens down and we can often find ourselfs in a deep state of relaxation.
Meditation is often more effective in the morning and can sometimes be done before getting out of bed, with the legs crossed and using the headrest or the wall as a support for the back.
If crossing your legs in the lotus position (or any near approximation of such) is uncomfortable, then rather don't and preferably find a comfortable chair to sit up in.