I was just about to make a thread on cloaking. If you use proxies, make sure they are Elite.
For cookies and security I use these add-ons in FF: Better Privacy, NoScript, Ghostery, Adblock. I always close the browser after I use a proxy to make sure my cookies are cleared and I clear all the cache. Make sure to always browse in private mode, never save history, accept third-party cookies from visited.
For the Agent I use User Agent Switcher add-on, you can download a whole list of user agents, you can access sites as a search bot, spider and a tons more. I usually just have it on Mac or Linux with FF or Chrome.
For proxy I use the add-on Best Proxy Switcher. You can go to a free proxies site, copy paste the entire page, put it in the add-on "Import proxy list", with all the text and everything, it doesn't matter and it will only grab the IP's and ports.
Good luck!