I am named as the inventor on a patent which is held by my employer, we have lawyers to do most of the law stuff, but they make us do a bunch of work first before we start costing lawyer time.
Searching for patents online is fairly trivial, but time consuming. I'm assuming you're in the US (I'm not, but the value of most patents is that they are not yet patented in the US, so we did our patent search there). http://patft.uspto.gov/
As far as patentable, I can't really comment. I am extremely disappointed that the Amazon single click purchase was awarded as a patent as I don't believe it is non-obvious. I'm not too far off the same belief for my own patent, but a bunch of experts had looked at the problem before and didn't get to my solution. They thought my solution was elegant and decided to patent it. At the same time, we mostly patented because that is what the higher-ups like to measure. I can't imagine my patent every actually being used for monetary gain.
So, you don't want to be a patent troll, but you have an idea. Do a patent search, see if it is already patented, but more important, do a search to see if anybody has come up with a solution that is close to yours. If the concept is already in the public domain, or something close enough, than you can't patent it.
The big question is why do you want to patent it. You say you don't want to be a patent troll. Will you be building a business around this patent? Can it be used in your existing business? Do you have the ability to make your invention into a viable product?
What is your definition of a patent troll?