Sit them down... then LISTEN

I'm going to admit to a lack of originality here.  The heart of this suggestion is stolen from one of my favored texts on working with human beings (Seven Habits of Highly Effective People, by Steven Covey).  One of his habits is "Seek first to understand, then to be understood."  There are so many reasons and examples I've experienced in my personal life why I have found this to be such a powerful habit.  The reason it's so important in coaching is you are trying to get a group of young people to listen to you and soak in what you are saying and believe it in a way you might not even expect from your own children.  (Remember, you are likely doing this at a time when every instinct in their bodies is telling them to forge their own way and test their boundaries.)
Question: How do you form this trusting relationship in a short period of time?
Answer: Find a way to show that your objectives are aligned, you are willing to listen, and you are on THEIR team.
Hint:  Don't make the assumption that it's only about winning games and winning a championship at the end of the season.  Remember WIIFM  (What's in it for me? And me is them!)

So here's the simple suggestion.  Set up a practice very early in your season (preferably before your first game).  Arrange for 1 or even 2 assistants to help you run a very pre-planned practice so it's easy for them.  Then you grab your clip board and go sit down in the grass somewhere (this gets you down eye to eye).  If you have the opportunity to use bleachers or another seat, you can do that too, but put them up above you.  In the scenario you are setting up, you are the one being spoken to, not them.  One at a time, pull each player from the general practice to come sit with you.  Then the big question:  What do you want out of this season?  What skill do you want to perfect?  or What weakness in your game to you want to improve (we all have them)?  Hone it down.  We want one thing.  We want the most important thing they want to work on (in THEIR game).  This isn't a conversation about team goals, but if you get a few of those all the better.  Take it all down on your clipboard, show you are listening and that this is important to you.  You shouldn't need more than a few minutes with each athlete, but you can see how this can take up an entire practice. Don't worry, it's time well spent.
Keep that list with you throughout the season.  Soon every note will be in your head as you watch and coach each athlete because you will be using it.  Take some time to plan specifically how to help them with their goal.  When you get those one-on-one opportunities, coach them up on their goal.  Commend their progress or make a suggestion how to adjust their technique to help them progress.  Now you are showing them that YOU are working for them.  You are listening to them.  It's a natural human quality that we listen to those who understand us and whose objectives we understand are aligned with ours.  Now you are working together and you are a part of THEIR team.