In the tabletop version I swore by my Undead team. Regenerate makes league games so much easier, plus they have access to the better parts of the sub-team rosters. They don't tank quite as well as Dwarves/Orcs/Chaos etc, but you gotta love a list that has S5 players as part of the strating line-up.
Played Chaos in the comp game. Tended to go for stomp and grind tactics.
In general, some good tips are, outside of the ones above...
* Assists are your friends. always try and have at least 1 per block (more block dice, less chance of catastrophic fuck-up).
* Make the opponent make as many dice rolls as possible. More dice rolls they have to make, the more chance of them fucking up.
* always do the important stuff (like picking up the ball) first
* push players off the pitch where possible. sure you don't get SPP for it, but that player is now gone until the half is over or a down is scored. Plus it's an automatic injury roll, so they might be out even longer