It would be ideal if you have established a close bond with your son/daughter in while growing up so that when they reach the puberty stage, they know they can talk to you. Of course, you still have to respect their decision if they are uncomfortable in discussing some things. As teens nowadays are very much different during our (my) time, learn to pick your battles. Save your objections for things that matters like drugs.
My daughter is still only a toddler, so I can't offer any personal words of wisdom. However, I think this basic parenting guideline handling adolescence should help! http://kidshealth.org/en/parents/adolescence.html
Marie Nolianne Ozoa