Yah, it's definitely worth milking the first few levels. I've been doing that. Unfortunately, if you milk them for too long, then you sometimes find yourself overwhelmed & can't finish the levels.
On the western saloon (first levels), I keep the top 3 bars clear by serving beers to those patrons as soon as they appear. I keep milking the bottom bar as much as possible, so I can focus on just that 1 bar.
Patrons reappear in the order in which you served them. So, if you go top to bottom with serving beers to patrons (early enough to scoot them out the door), then they'll reappear in that same order. It makes it easy to keep track of them if you're organized.
My biggest problem is picking up a tip & then instantly serving a beer, without waiting to see if the patron turned around to watch the dancing girls.
Oh, and picking up tips is big points, but it totally messes up my organization method described above for milking, since some patrons watch the show & some don't. Everything gets out of sync & messy when I pick up a tip on a higher level (stadium).
My 2nd biggest problem is tapping up or down to move & assuming the game registered the move but didn't, & I find myself serving a beer to nobody...
I'm well into the punk levels & got 80k+ so far for my best.
Thanks,
-Jason