I suggest to play on Highway and always try to eat all the dots and never use bombs.
You'll need 4.100.000 points for the S Rank.
When you eat all the dots you'll get a bomb and the more bombs you have at the end of the round the more bonus you get. Also, the longer the chain of dots you eat is the more points you get per dot. You'll also get bonus points for your lives at the end of the round so don't lose one.
By following this strategy I made just a hair over the S Rank point mark. The normal stages are easy to learn, the ghosts will always walk in the same directions if you eat the dots in the same order. You'll rarely have to avoid angry ghosts. What makes and breaks the run is when you have to eat the chains. You need to do good on these to get far enough in the alotted time.
Wish you best of luck with this.