Instead of harshly imposing the rules and regulations to be followed, you should convey these politely. Explain to him/her about the importance of these rules and teach him/her what kind of behaviour is acceptable in the society.
One should not be merely involved in dictating terms but also focus on spending quality time with the teenager. Try playing favourite sport with him/her and do consider watching meaningful movies with them.
Children adapt what they see, so be careful with that. Treat them with love and avoid arguing or fighting with your spouse in front of your children. Try to create an ideal family environment as this would have a nice impact on your kid.
Emphasise the need for positive behaviour and do not forget to appraise the teenager if he/she is doing good things.
You should also make sure that their bad behaviour does not go unpunished but there should be a line for strictness.
If your teenager is way out of your hands then you should counsel him/her without wasting time to avoid future troubles.