[rvern]

In Mozilla Firefox, you can create the setting general.useragent.override (it doesn’t exist by default) and set its value to “Firefox” to get a very generic user agent string that websites will still recognize as Firefox and not block as a bot.

Regarding plugins, the best solution I have found is to have none enabled. Firefox still sends them in the list when using click-to-play, so it is necessary to disable them completely.

[ryan-c]

As I said in my other comment, changing your user agent string affords you no privacy protection against those who care about knowing, and makes you more trackable.