G Protein Coupled Receptors Table

I tried to find a mnemonic for this complicated counter-intuitive table but I failed.
The information in this table is really high yield and we have to memorize it by heart for USMLE Step 1.
There are things that are self explanatory such as M2 is coupled to an inhibitory G protein (Gi) because muscarinic stimulation of the heart is inhibitory. Another example that makes sense is that alpha2 receptors inhibit insulin secretion so it is Gi coupled.
However, we can't just understand how Beta1 (stimulatory) and Beta2 (vasodiltor and inhibitory) are both working with (Gs).
Bottom line, you have to memorize the table by heart and I don't know how you'll do it.

Here's the table:

Click on thumbnail to enlarge