I use reversed cards, and I generally interpret them to mean that while the energy is active, there is something blocking or negating the card.  For instance, a reversed Chariot in my readings usually indicates that a person will travel or purchase a new vehicle- but it also warns that there will be obstacles, delays and problems related to that situation.  A reversed Empress indicates a person is anxious about the possibility of pregnancy (usually, but not always, unintended pregnancy) but they are not, in fact, pregnant.  A reversed Tower is a situation that is teetering on the brink of collapse- a situation in which all but the essential could easily be lost- but something is managing to keep it stable, at least temporarily.  A reversed Death is a situation in which a person is ready to start fresh, but there is unfinished business preventing the situation from reaching its natural conclusion.

Never get nervous about the cards!  If you're unsure of a meaning, you can always use a card as a significator in another reading to help get a fuller understanding.  And ALWAYS keep a journal- it helps to recognize themes and patterns and gain better insight into the symbolism of the cards.

Sometime at the beginning of my studying Tarot, I decided to use the revearsals. It suddenly got me 78 interpretations to learn + other 78. It didn't bother me much... I like the revearsals because they give another understanding of the cards (as previously said). It's not like the normal position is + and the revearsal is -. Well, they sometimes are, but they can also be another viewpoint. I can't say I recommend them, it's a lot more to learn, but I do prefer them for myself.

FV and Sonia sum it up all very nicely. I also find that reversals give me a lot more to read, so I get twice as many meanings for the same price!

Of course, I can see that is exactly what throws back most readers from reversals: 78 meanings is more than quite enough to learn! Well, yes, but the point is, we are not supposed to be learning meanings by heart, are we? So you should look at a reversed card and wait to see what it tells you.

I find reversals quite useful in fairly big spreads, because they give me a general impression of tiredness or blocked energy from the querent, specially reversed wands. A lot of reversed cups make me think of someone who has been deeply hurt emotionally and is now guarded and distrustful. Reversed swords bring me a sense of confusion and lack of vision at the moment, while reversed pentacles can show a low time in practical or economical matters.

Then, when reading them one by one, you get meanings like those described by the above posts. In fact, reversals can lessen the impact of some quite negative cards, as they show the querent fighting to leave the negative situation behind or solve the problem at hand.

However, Tarot reading can be quite daunting at first and 78 cards are more than enough to tackle at first. I would leave reversals for the time when you feel confident enough with your deck and start feeling some curiosity toward reversals -for many, that never happens and it is fine-.  

The funny thing with revearsals is that I usually get them in times of bad emotional times or when I am blind about certain things. When I'm balanced and calm the cards miraculously turn back up. I have to add that it doesn't affect the readings and interpretation, it's just a subtle way of the deck to tell me there is something rotten in the state of Sonia