BODY: the immediate effect of meditation on your body is a feeling of relaxation, ease, and comfort. You will feel this in some level from the first time you meditate. As the months (and years) pass, this becomes a skill that you are able to tap at will at any moment during your day. There are also several benefits to your nervous, respiratory and circulatory systems, that you may feel or not, but that nevertheless happen.
MIND: meditating is like giving a break to your mind – or taking a break fromyour mind. In the first months/years you may feel the mind gets more active during meditation. In fact that is not necessarily true – it is only that now you are paying attention inside, instead of outside, so you see better what was already going on. If you continue practicing regularly, however, you will see that meditation become a space of refuge and nourishment. You will feel it improving your clarity of thought, memory, power of concentration, and resilience.
SPIRITUAL: for those that are into these type of things (like I am), meditating regularly is by far the best thing you can do on your spiritual journey, and, in many traditions, is almost the whole journey on itself.