Every game needs a screen to define what button does what in the game. It helps for those moments when the player is scratching their head going, now what button did what again?! So when you're creating your game, you're going to want to take a little time to add that screen into your game. Or if you feel like using my code, you could spend an even smaller amount of time!
Recognizing that I was going to be making this screen often for all of my sample games I release for my site (I'm working hard at trying to get them to follow the Best Practices release by Microsoft for XBLCG). I took some time out and wrote this dynamic "How To Play" screen code. Simply define text for any of the controller buttons and this screen will display that with a line to the appropriate button.
Check out the sample, "What Button was that?" and use it in your games. Play with it, enhance it and let me know what you think!
Also, before you get going, you should think about what controller buttons you're planning on using and what you're planning on having them do. Then take a trip over to MVP Jon Wattes's site to read up on the expected button actions and try to make sure your games controls are staying consistent with what players expect.