When using the Elliott Wave Theory, I think the most difficult task is to be objective. Is this a third wave or an ABC or correction? Is this a long drawn out two wave or a slow forth wave?
First, and most importantly, when counting waves the direction of the market must be identified. Identify if the market is a bull market or bear market. 
After identifying the primary direction, figure out the impulse waves (waves 1, 3, and 5) and your countertrend moves (waves 2 and 4). The wave that I try to start with when working on a count is the third wave. Beginning with the third wave is the best place to start, because it is often the most dramatic in a wave sequence in both intensity and point movement. It is “easier” to identify than other waves. Notice the dramatic third wave in the NASDAQ weekly chart below. It is labeled with an arrow.
The hardest part about wave counting is to stay as objective as possible. For example, if you think the market is going down, then naturally you are always trying to find the impulse sequence on the way down. However, if that is not what is happening in the market, then force yourself to be honest. For example, if you have to keep changing your wave count to fit the charts, maybe you should ask yourself if something else is really developing. I'm always "checking" myself and making sure that I'm not seeing something that isn’t really there.
One way that I use to figure out if I have a correct wave count is to analyze the social mood by using headlines and television commentary as my guide. For instance, the other day the Goldman Sachs CEO said that banks do "God's work." That type of comment seems a little extreme to me, so that could be a great starting point for a market "top." Whether or not the market falls thousands of points from that point or a few hundred, or not at all, that type of comment would be recognized as an extreme example of a headline, and a possible place to get short. On the other hand, back in March when everyone was calling for Dow Jones Industrial Average to fall to 4500, that was a little extreme on the downside—thus, time to get long.
Last comment: It takes extreme concentration to stay focused on what is at hand and not "what could be."
