It's a bit hard without the on-court displays or animated diagrams seen in more recent games. I'd suggest looking up the plays on YouTube to see how the players and ball move and try to replicate it in game. When you call a play your CPU teammates should get into position, but that should help you in terms of starting in the right position and what to do next.
When it comes down to it, NBA Live 07's playcalling is nowhere near as deep or effective as what you see in NBA 2K11 and NBA 2K12, or for that matter NBA Live 10. You can see how well they'll work out for you and get an idea of how they work through simple experimentation, but don't expect anything like you'll see in more recent games.
Set the difficulty into easy and play a game, If I remember correctly, hints show up at the bottom of the players when you call a play at that difficulty.
True. In recent games where playcalling is deeper and more functional - and the CPU also does a better job of running plays - it's worthwhile bothering to run a diverse set of plays. For NBA Live 07 PC though, basic quick plays like Post Up and Pick & Roll will still let you get the job done.