The perfect world:  You know what your kids are up to and have some insight to what they are doing all day.

Our world: Kids and parents find themselves going in ten or twenty different directions having absolutly no clues as to what each other is doing.

What is a hobby: a hobby is something one does or one is interested in that can and most likely will define an outline or guide to one's future.  Knowing your kids and knowing their hobbies could be a step towards knowing them and who they are.  Today we don't know what our kids are up to, who they hang out with, why, where..., one way I know to get to know someone is to become interested or at least help in a hobby.  I find one great way to start is to simply sit down and write a list, or perhaps even have your kids write a letter of what they like or are into.  Find a lot of this item or these items for sale, me I collect rocks, wolves, and some antiques.  I take and buy a lot of so uncut unsearched gems or of rock beads and I sit down and sometimes spend hours sorting them into containers.  It may seem like the most boring thing you'll ever do but this is the time to talk or have a conversation, " hey what's up at school, how's it going, doing well in your studies, any problems"? 

A simple conversation over sorting rocks..., one that could open a whole knew view on your kids' lives.  I never know there was a bully problem till I got to talk over a bucket of rocks, I never knew there was a failing grade till I got to talk over a wolf figurine, and never knew where they went or how they got there till I got to talk over a box of old tools.  The most important conversation can be held over a little treasure, maybe your diamond in the dirt is a collection of dolls, marbles, toy cars, trains, or even canning jars and buttons, what ever the hobby, getting involved in it can open so many doors you'd be surprised.  It may be to most important thing you will ever do with your kids, take that time and get involved before they grow up and leave you wondering what happened and where they went. 

These things take time, don't just buy a rock and ask, "okay where've you been and what've you been doing", take your time and enjoy the company while it lasts.

P.S. love your kids while you still have them.