I played the way you advised here - played it about 5 times - and still cannot beat 18390.
I am very curious as to how anyone can get 20000 on this level and would so love to hear their detailed walkthrough. If you did get 20000 using the exact steps you posted above, then either your computer is faster or maybe random events like the number of spills you mop up are adding to the points...I noticed the amount of spills vary from game to game and add a different number of points.

Suze,
There's no question about it--this is a REALLY hard level.
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There are two different walkthroughs posted in this topic--did you try both of them? Jen's will get you more points, but requires a faster hand. Mine will just barely make Expert, and even then only about 1 in 3 times, but WILL work for slowpokes eventually. As you point out, the randomness of the water spills can throw this one off.

Yes, I tried both techniques offered here and only got just over expert. I want to get better than the 18,000 or so I had at my best, as I know it must be possible to get higher scores on this level. It's a matter of personal satisfaction in achieving a better score when I try again and strategize better.
I am sure a lot of you feel the same way! You may get just over expert, but then you feel challenged to do better. This is how I was on the first 2 DD games. Over 2 years I kept re-playing levels and crossing out my high score and writing new high scores. There is no master list of absolute highest possible scores and because of the randomicity on some levels, perhaps there never can be.
Oh well I take this game too seriously and always have. But for me it's a puzzle I enjoy solving.

I finally made expert in this level. I started out with Jen's technique but wound up using my own. The main key to my getting expert is I mentally forgot about the people in line. With this level there is nothing you can do about them anyway. I even put my left hand over the line of customers where I wouldn't pay any attention to them. Don't laugh too hard. It worked. lol

argh tearing my hair out playing this level !!!!!!!! keep losing people from the line

tried both methods and can't do either boo hoo :-(

I did everything Jen said and just managed to pass with an expert score.  I got everyone seated and served as good as I could but still lost the 2 teenage boys near the end.  I think if I hadn't I would have gotten at leat 18000 but i got 16575, which is still expert and all I was going for anyway.  Thanks Jen, your walkthroughs always help!:)

Thanks Jen! That helped me out so much! I can't make expert, but at least I made it! I was stuck on that level for way too long!

That's an impressive score, Jen.  I've only reached as high as 27,000 points and have not been able to repeat that process.  That constant mopping sure helps getting in those extra tips.  I noticed that also, when you seat new customers and there's a wet spot already, you can then mop the floor and the customers hearts still increase.  Go fig.