Just study the backlinks of your #1 competitor using tools like ahrefs and seospyglass. Thats usually what I do (ahrefs is a lot more accurate).
I don't usually pay attention to anything other than that.
Sometimes you will find sites that block their links (like my own sites rank #1 but display 0 links in all backlink tools)
and those are a PITA to deal with. But most of the time all I use is ahrefs. I don't care about the volume of results,
or PPC competition, the ONLY thing I care about is backlinks, what type, how many, how their anchor text is done,
pr of their backlinks, pr of the page, and I basically graph all these factors in my head then determine whether I
can outrank them.
There are much more sophisticated ways of measuring competition (I think moz has a tool that gives a site a
number). And people who have private networks will know if the number is less than a certain amount, they
can rank for that keyword (depending on how strong their network is).
But for low to moderate competition keywords, I always just check backlinks in ahrefs.
-SB
