Levels Tips Credits

The formula for calculating the rank is as follows:
Captured Ghosts x 120 + Collected Treasure - Time in Seconds - Health Lost * 6

This means:

• A ghost is worth 2 minutes
• One gold coin is worth 1 second, a note 5 seconds and a gold bar 20 seconds
• You have to be 6s faster to make up for each lost health point

The strategy to get a 3-star rank usually comes down to getting some gold, being fast and capturing ghosts in the ideal way.

Capturing multiple ghosts at once gives an additional gold bar for each ghost.
Capturing a ghost with a surge gives the following:

• A level 1 surge drops 3 coins
• A level 2 surge drops a gold bar
• A level 3 surge drops 3 whole gold bars

So the goal is to always capture multiple ghosts at once and to capture them with a surge.
Greenies can barely be captured with a level 2 surge, all other ghosts can be captured with a level 3 surge.

Knowing gold locations tends to not be too important, you usually only need to get the obvious gold locations on the way and look up whether the level has Gold Greenies (Mariowiki list) or a Bonus Challenge (Mariowiki list) as those give a lot of points.

Catching a boo usually doesn't matter either way, they give roughly enough coins to make up the time spent on catching them. Get them if you need them, otherwise ignore them.
Gems on the other hand are a de-facto waste as they don't give any points. You can still get them if you need them though, most levels are lenient enough for that.