Quoted from goatdan:

If you become decent at it, the ball locks are really easy to hit, so the strategy for points is plunge ball, lock ball, plunge ball, drop target, hit ramp to start multiball and then shoot balls past the spinner to build 7X bonus and then up the ramp for points. You can also shoot the ball up the other ramp to keep switching to "Extra Ball" as the SHUTTLE reward.
If you lose a ball, catch and lock the ball and repeat.
It's a really, really simple strategy, and if you have decent ball control skills, it makes it so that you can play for a really, really, really long time. And with the ruleset being so shallow, playing that long isn't so rewarding. There isn't really anything else to shoot for.
It doesn't help that the game has the Airlock thing that saves the ball and the up post in the middle of the game.
And again, lest anyone think I'm trashing their favorite game or whatever, I really like it for what it is. I am waiting for my new tumbler to arrive tomorrow for the playfield swap that I'm in the middle of to continue. But I also realize that Shuttle will be one of the games that I have in the collection because it is a looker and something nostalgic (it's the title after Jurassic Park that I credit with getting me into pinball), not because it is a great playing machine.