NEW YORK ( TheStreet) -- It is beginning to appear that the market is entering into a sideways trend after a nice six-month rally.The S & P 500 started rising in October of last year and more than likely peaked (for now) at around 1,422 back in early April. It looked like maybe the market had some rally left in it, but then more bad job numbers and a political sea change in Europe snuffed it out. Apple ( AAPL) was one of the poster children during this rally that took the markets on a 30% run. I was able to cash in on stocks like Apple, Tractor Supply ( TSCO), Dollar Tree ( DLTR), Ross Stores ( ROST), Sturm Ruger ( RGR), Alexion Pharmaceuticals ( ALXN), Terra Nitrogen ( TNH), etc. during this up trend. I like to own leadership stocks in the portfolios that I manage. I define leadership as stocks that possess performance (momentum), value, and have healthy stock charts. Fortunately, leaders can be found amongst all different style categories, from aggressive growth to conservative growth and income stocks. I have my own proprietary ranking and grading system that I use to select my stocks. I try to stay within my top 200 ranked stocks. This eliminates just over 2,600 stocks from consideration and makes my job a whole lot easier. Once I have constructed a portfolio of about 25 equally weighted positions, I check those positions daily for performance, value, and the health of their charts. In recent weeks, I have been noticing some market rotation taking place. This recent run in the market has greatly favored the more aggressive growth stocks which performed so poorly in 2011. In fact, 2011 was a year that greatly favored large-cap dividend paying stocks. Then they began to become pricey in late fall of last year and started dropping in rank. More aggressive growth stocks like the ones mentioned above began to pick up the leadership baton and run with it. I have been able to bag some big returns during this most recent run, but as market rotation begins to now set in, it is important to watch for tired leaders begin to give up the ghost, while new leaders begin to emerge.