Because of this, I always try to light ESCAPE first. I've got mine set for no extra lives, but video mode is pretty easy. Also, I've got mine set so that the game doesn't self-adjust, so you always get e-ball on wave 2.
I always try to complete 2 vid waves, lighting Dr's 1 and 7 and 6 (and e-ball) before going for the locks. If I accidentally get a lock, I switch to Dr. 7 so that 6 is lit on the nex vid wave. If 6 and 7 are lit, I go for Dr. 3 next since two W-H-O loops gets an e-ball.
Once the balls are locked, I focus on O-loops to get my multiplier to the max. If I get to 4X before getting to multiball, I try to finish up the rest of the first 4 vid waves for gratuitous, easy points.
Having saved the best for last, and making an occasional O-loop to keep the multiplier up, I go for multiball. When the balls release from the locks, I let all of them dump down the drain since I know I they will be given a 'second chance'. This way, I can try and avoid the chaos of keeping 3 balls on the table since the machine is forced to serve the balls one at a time.
If I am making my shots, this works great... get each Dalek one at a time... when the next ball comes, I try to send it towards the jet bumpers while the mini playfield does the down-up thing. If I'm luckly, the jet bumpers won't eject it onto the playfield and I won't have to manage more than one ball at a time.
Of course, this is pinball... it is not long before I miss a shot, lose control and all havoc breaks loose. If I am lucky enough to catch a ball (or two) on the left flipper, I hold it there and try to make the Daleks with just the right flipper. This technique gets shot to hell as soon as I miss a Dalek shot and I need to use the left flipper. I usually lose them all shortly after that.
Another neat trick: If you get a quick re-lock, don't shoot the ball and eventually the locked balls will come down... keeping you from having to manage the third ball which remains in the shooter lane! There is some disadvantage to this, but I can't remember what it is.