It's really dependent on the person as to what is a better method than another and it is perfectly acceptable to meditate lying down (simply watch out for falling asleep). There are even people who can meditate while jogging or dancing - the point is that you are in a meditative state and there are literally thousands of ways to achieve that state.
If you feel meditating laying down fits you best, then goo for it! We all have our different ways of meditating. Be careful not to fall asleep though. It is up to you how you wish to meditate. I personally meditate sitting up and listening to alpha waves.
I have a really hard time meditating ,I'm not sure why, but I try all sorts of techniques (that can be done all sorts of ways). Rhythmic breathing eems to be the easiest for me, but I do sometimes need music of a consistant type ( like ocean sounds, or rain, or drumming). Theres the times soo much is going on around me, its easier to meditate than filter thru everything. I also, never fail, dance. Turn up something you can get down too and dance , its great at "letting it all out". Numerouse Native American cultures are known for this. You dance till your so exhausted you dance more and as you reach a heightened state of consciousness, boom , your where you need to be , whether it be meeting your totem creature spirit guide, (or the hospital from dehydration) or just relaxing finally. Theres also breathing techniques, like in one nostral out the other, but I'm not great at it, its a yoga technique if you're interested. blessings