I hold between a few weeks to a few months which is somewhere between swing trading and position trading I suppose.
I'd rather not tell everything about my system, but I'll give the gist.
Every now and again I'll review about a hundred different sector indexes (I like the DJ list at
http://www.investorideas.com/Research/Stock&IndustrySectorIndexLists.asp) to see where the momentum is (I use a % based charts for this..
http://stockcharts.com/charts/performance/ is a good resource for this). Then I'll make a list of the top 5-10 sectors. Then I'll sit on my hands until one of them makes a fast move contrary to the prevailing trend (as shown by a long-term moving averages). The faster and bigger the better. I like a Full Stochastics indicator with high numbers for helping to gauge the general bottom (don't use the same indicator for selling as it will go off prematurely.) I've attached a picture with a Full Stochastics indicator pointing to long buying points on the 'hottest' sector available (coal). The faster the index/stock is trending, the higher your settings must be to get signals (I keep multiple up). I also like to keep an eye on the speed that the price is declining: if very fast then I want to see some slow in the momentum of that mid-term trend; if very slow then I may stay away as the long-term trend could be bending. That being said, timing is a lot harder then finding and getting in a good long-term trend.
Once I get the go-ahead on the sector level, then I'll start looking at stocks inside that sector. Unless very speculative a company, stocks tend to trend quite noticeably with the sector index. I basically do the same thing there.
Use stops. 1) they let you invest in the several very best opportunities rather than heavily diversify to hedge the total risk 2) they let you stay active, rather than becoming an investor to a fallen stock 3) they could save your emotional life. Beyond hiding them behind a big round number if nearby, I think that stops should be based almost purely on capital preservation rather than strategy: IMHO, it's just too hard to predict movement over a very short period of time.
I also put a little bit of weight on fundamental analysis of the stock. I'm a big fan of PSRs and PEGs.