First, install Doppelganger. Instructions are below.

Doppelganger should start by default. On the first run, it will ask you for your name and email IDs. You should enter it like "Umesh Shankar ushankar mysecondemailid". The idea is that it tries to detect certain personalization and auto-login features automatically using this infomation.

Doppelganger adds a couple of buttons, a status message, and a checkbox to the status bar.

(You can leave checkbox labeled "debug" unchecked unless you are very curious or want to examine Doppelganger internals. If you do open the debug window, be sure not to close it directly; instead, uncheck the checkbox in the browser.)

The first button is labeled "Paranoia" and lets you control how Doppelganger handles first-party session cookies. (Third party cookies are all blocked by default.) There are three paranoia settings: high, medium and low. You probably want medium or low, which will automatically enable some or all first party session cookies, respectively. With the low setting, you will get only a small number of left-or-right dialogs, corresponding to useful persistent cookies set by sites you visit. With the high setting, you will get the maximum control over session cookies, but have to answer more questions. So there is a tradeoff between increased privacy (paranoia) and ease of use. Doppelganger always asks you to choose for persistent cookies, though.

The next button is labeled "FIXME". It's used to recover automatically from the situation where you need cookies to use a site, but they were not enabled for some reason. More details are below.

The status message shows the status of the hidden window relative to the main one. "Sync" means the two windows are in sync. "No sync" means there was an error loading one or the other page, and Doppelganger won't be able to do its automatic actions. "Loading" means the fork window is still loading the current page. And "Fork off" means the fork windows has stopped mirroring for one reason or another (a decision was already made, you spent a long time at the site, etc.). The main thing to note is that

You can browse as you normally would. When you visit a site, Doppelganger will mirror your actions in a hidden window, looking for differences between the hidden window and the visible one. If it finds a difference, it will --- depending on your paranoia setting --- show you a side-by-side view of the two windows, along with a description of the privacy risks you face in switching to the content in the (heretofore) hidden window. You have to decide if the privacy risk is justified by the additional functionality. If Doppelganger can figure out what that additional functionality might be, it will highlight it on the right-hand page.

If a site does not work properly (e.g., doesn't log you in automatically when it should or there is an error message telling you to turn on cookies) Doppelganger should detect it automatically. Sometimes it won't, for various reasons.  In those cases, you can click the FIXME button, which tells Doppelganger that something's wrong, and that you might want cookies enabled for the site you're at. Doppelganger will take some action to resolve the problem, possibly replaying your session at that site to get you to a good state. In some cases, cookies may be enabled already, in which case Doppelganger probably cannot fix the problem on its own since it's not cookie-related.