1. Easy cards are color to color ONLY
2. Medium cards are shape to shape or color to color ONLY
3. Hard cards can be any combination
If possible, look at the greenhouse or other possible tile placements to help limit choices.
If you can narrow down the options to 50/50 it is worth guessing if the queen is moving at speed 1 or 2. Later, it is too risky, unless you are significantly ahead!
Early on (when the queen is moving at only 1 space), it is sometimes worth guessing on a tile with multiple options.
Game phases
The board is broken into legs, separated by the checkpoints where the Queen gains an additional step to her movement.
First Leg
The goal of the first leg is to fill as many tiles as possible. During this leg, an easy card should always be chosen and the rest should all be medium. Only one card should be guessed per player turn; this will keep the player pawn in the first leg longer, allowing more tiles to be filled. Missed guesses are okay in this phase since the Queen will move only one additional space. Building rings (see below) should also be prioritized over guessing cards if a good placement for card information isn't possible.
Second Leg
The goal of the second leg is to maximize your lead over the Queen. Avoid situations where no guaranteed guess can be made. Use your best judgment deciding between guessing an additional card per turn, or leaving it as insurance for the following turn. When choosing to guess only one card, guess the card of the player who's turn comes up the soonest. This way, when it is their turn, they'll have a fresh unguessed card to place a tile for.
Third and higher Legs
The main goal of each leg after the second is to minimize how much the Queen will catch up. The Queen will certainly be closing the gap you created in the second leg. By now, she moves the same, or more, spaces as a medium card gains. At this point, it is critical not to miss guesses.
Building rings
While placing tiles, try to make rings as you go. The center of the rings are powerful spaces and should be saved until the third leg where missing guesses is punished more severely.
To make a ring powerful, try to diversify the shapes and colors around the center point so that there are unique values for each number that would appear on a block.
This ring has been designed so that a value of 2 can only be Heart, a value of 3 can only be Pink, and a value of 4 can only be Diamond. For a card with Hearts, Pinks, or Diamonds, this spot is immensely valuable.
Try to make multiple rings around the board just like this, but with different guarantees. For example, if a second ring is made where 4 must be Purple and 3 must be Spade, then between the two rings, any card with Spades, Diamonds, Hearts, Pinks, OR Purples can be a guaranteed guess.