A few tips off the top of my head...
1. Play your modes. Some of them can be exceedingly valuable as far as points are concerned. In conjunction with modes, pay attention to those playfield multipliers. You can get it up to 6X, I believe, which can be huge. If you're having trouble beating a mode, stacking it with a multiball can make things a little easier; modes will continue during any multiball mode.
2. Always make sure you get skill shots. They are worth 10% of your score, usually being in the upwards of tens or hundreds of millions for me. Essentially, as you play the game, you're constantly building your skill shot value. An easy skill shot for me personally is the right "Who Brought the Dog?" orbit-- hold the left flipper and plunge all the way so the ball can bypass the "P-K-E" lanes and loop around the game. Then, I try to get control of the ball and make the right orbit. It's a pretty easy shot to make for me. Skill shots with the mode inserts in front of it will also start modes, so if you constantly make skill shots you won't have to worry as much with shooting for the dangerous Slimer to light them normally.
3. Watch your ghost count. Collecting enough ghosts will enable certain high-scoring features, including "Loopin' Supers", "PKE Frenzy" and -- finally -- "Mass Hysteria" multiball at 100. The first two modes are especially huge scoring opportunities and shouldn't be missed.
4. Go for Storage Facility locks. Just like what you said you've been doing. The captive ball must be hit once to light lock, then once again during a sliver of time to light the lock. Collecting enough ghosts also light locks for you, but if you're having trouble collecting ghosts then I wouldn't rely on that-- captive ball seems better.