How to you effectively measure your SERP competition?

What I means is what are the first things you do when thinking about entering a market?

Check top 10 sites for PR, Age, Backlink Count, On site SEO factors (KW density, Images, Videos etc) is what I already do but is there more I should be looking at?

What I usually do before I decide to use a keyword is:

-Check on google how much is the monthly search volume
-Put the keyword in a market analyzer tool (like Niche Market Finder, its free, google it)
-I then check on my affiliate company (this one is up to you, i use Comission Junction) how much % is commission, if they pay for leads, etc.

Thats pretty much it bro...

Hope it helps

Thanks! I'm part of CJ as well and feel confident now that I'm checking the right things.

I think you can base on the competition of keyowrds that your competitors rank, also check backlinks. I mean quality backlinks (most of them from EDU, GOV and high PR and alexa...). That is it. Or you can check how many articles that they wrote and submitted to popular sites.