how about having a option (default on so only non newbies turn it off) that shows tooltips on the screen, for example. If enabled and you spawn in goal "Do not leave the goal, you are keeper" will appear on screen, in reasonably big letters.
if you lock on to someone "right click to pass" will appear
and so on and so forth
when i player gets within a certain proximity to the goal with the ball "Back to goal, defence needed"
when an attacker gets close "goal being attacked" etc..
they'd be nice if a pop-up type box was implemented for them... if its just a flash of text accross the screen, it becomes annoying. Containing it to a small portion of the screen is very important.