Hit / Campaign Parameters
utmcc contains the combined strings of the __utma and __utmz Google Analytics cookies. This string is URL encoded.
The utmcn and utmcr parameters never appear in the same request and both only appear with a value of '1'.
The utmip property can be anonymized by removing the last octet.
Event / Custom Variable Parameters
utme can contain data for Event, Custom Variable and Page Load Time tracking requests.
e-Commerce Parameters (Transactions)
The utmtid order ID must be unique for each order, otherwise Google Analytics will group multiple transactions under a single entry. All monetary fields should be filled in without a currency symbol, e.g.: 12.50
e-Commerce Parameters (Items)
The utmtid order ID parameter must match the one used in the _addTrans() call this item belongs to, otherwise it will not be associated with the order correctly.
These values are sent by _trackSocial requests only.
utms increments with each successive request made for the current session. After 500, hits will be ignored.
The guid parameter is used as part of creating the Visitor ID and the guid=on parameter is typically sent by the mobile version of the Google Analytics tracking code.
Cookie string values
These values are not sent as parameters, but are encoded into the utmcc cookie string that is sent as a parameter in utm.gif requests. These values are contained in the __utmz campaign cookie and will not be sent if this cookie is not present.
utmcc also contains data from the visitor cookie, __utma.
Google Analytics UTM Parameters (v2) Cheat Sheet by Jay Taylor
A guide to the parameters sent with all requests to Google Analytics via __utm.gif