One strategy is just to rack up big mode points beforehand, since the base shot value is derived from a percentage of your multi-kill shot score, which itself is derived from your score in the modes. Generally anything over ~1.5 million is really good.
Other than that, it's pretty much 'survive and hit shots'. On a premium/LE, rack up the bombs and hope you have enough to cover the remainder of that wave if you drain the last ball. 
Also if you're pretty much about to die and you're not confident you can hit the shot you need, just sacrifice yourself so you're not sacrificing your ball too. (say: you miss the shot and it winds up draining).
The "super jackpots" after each wave keep gradually increasing too.
