Today started with a gap of over 1% and good earnings news from Intel which are often catalysts for the formation of a trend day. Trend days can make your week or even your month if played correctly so it is important to be able to identify one early in the day so that you can take advantage of the easy pickings during the rest of the day.
If you just focused on price alone, you really have no indication that today is not a trend day (as of 12:00 pm EST). We had a large opening gap, and price hasn't crossed the 20 period moving average (green line). It seems that the bulls are in complete control, and the news is hailing DOW 10,000 before it even happens.
But when you look at market internals you'll see a different picture. The NYSE TICK is a great tool for understanding what is going on "behind the curtain".
I've posted a capture of the NYSE TICK which shows that caution should be taken in assuming this is a trend day. Usually on a trend day you'll see extreme readings on the TICK (above or below 1,000). The green line is +1,000 and the red line is -1,000. As you can see, the TICK has not reached extremes on either side of the spectrum. To me, it looks weighted on the sellers side, especially during the first couple hours of trading.
Currently, it looks like TICK is hovering around the "zero" line which indicates this day is more like a "range day" than a trend day. Using tools like the TICK can help you make better decisions about price structure and allow you to determine how aggressive you want to trade. On a trend day you want to go nuts and risk a lot to make a lot. On a range day, caution is the theme of the day and you should trade much more conservatively.
As always, it will be interesting to see how the day plays out.