Just to clarify when do you use formal language in Russian? would you be expected to always use formal language when meeting a new person or is it ok for two people who are the same age to straight away be informal? what is just a basic guideline on when to use formal language or when it is ok to be informal?
every time when you want to be polite with a person ( doesn't matter what age etc) you should try to speak more formal especially with unknown people. and you can be informal with people who are just your friends.
If you don't know each other its ok to be informal If you're the same age. But if you talk with boss, with teacher and the reason of your communication don't related with personal life you should be formal.
There are some cases, then unformal speech isn't rude and ignorant to unknown people, but there aren't any rules, all depends on persons and conditions. I think, while you learn the issue, should come to unformal speech after native speaker.
