If you're not acquainted with an adult person (for a male person of your age that would be males in their 30's or above and females in their 20's or above), it's socially inacceptable to address them with
ты, though acceptable to respond them with
ты once they started first.
For persons of both genders in their 50's or above, it's non polite to call them
ты ever (even if they do).
This is especially important for communication between two genders, as an attempt at shortening the social distance without a practical cause (like a work relationship) can be considered as an invitation to romance, so you should not do it unless you mean it.
There are few exceptions to this rule, which, nevertheless, should be used with care:
- In team games of sport, like football or volleyball, you address a member of your or opposite team with
ты, even if they are significantly older. It does not apply to calmer leisure activities like fishing or cards.
- Male drivers tend to use
ты more readily when addressing each other (asking for help or directions). A phrase like Не подскажешь, как проехать в центр? is considered acceptable between two drivers of your age but sounds quite rude between two pedestrians. Some consider this practice derogatory, so it's safest to address people when driving the same as you would do when walking, but mostly it's not a sign of disrespect.
- An Orthodox priest addresses a member of his parish in a church with
ты and they respond him with a
вы (regardless of their age and gender). Do not be surprised when visiting churches.
- Really old people could address you with
внучек, especially when asking for help (Сынок, не поможешь донести сумку?) . It would be acceptable to address them back with
дедушка and use singular verbs and adjectives (Конечно, бабушка, давай свою сумку). But it is not polite to address them like that first.
In all examples before,
вы could be used instead.
All these examples concern addressing complete strangers. If you're acquainted with a person, more complex rules apply.