You can check the page source and if you get something like rel="nofollow" or rel="external nofollow" then it means that that link is nofollow. You can also use plugins for your browser. I'm on Firefox and Searchstatus works just great for the detection of nofollow links.
Its even easier if you are using chrome, or firefox with the web developer plug-in (called firebug) Simply left click on the link and select "Inspect Element" - Then you can view the link source, and quickly see if it includes rel="nofollow".
I think using SeoQuake for chrome can really solve the problem for you. It simply strikes out the link that is no -follow. Link for seo quake is: www.seoquake.com; open it in chrome and it will show you how to download it and use it.
I use a firefox extension called SearchStatus. Every website I visit, any no follow links are highlighted in red. You can turn this off at anytime which is nice. It also displays the page rank. It makes my life really easy!!
Well yeah I agree but I use chrome because I think firefox is a bit lazy...and their chrome version is working just fine although still in beta.
I think seoquake or seo4firefox add-on would be really useful when you are on your targeted pages while backlinkwatch would be helpful if you want to see the overall backlink status for a competitor's site. Wish this help,
As has been said, SearchStatus will easily display all nofollow links on a page, and can be readily turned off. It also allows you to see an instantaneous link report of a page, which can be helpful. There are several tools built into SearchStatus... I highly recommend you check it out. It uses very little memory, and is always at your fingertips.
If you're talking about nofollow links that point to your page, no, they won't decrease your ranking. But they will not pass any link juice on to you, from the page linking to you. Obviously, they can bring you traffic.