What should be done after shaking the Margarita ingredients in the stainless steel shaker?

After shaking the Margarita ingredients in a stainless steel shaker, the correct step is to shake and strain. This process is essential because it incorporates air and chills the mixture thoroughly. The shaking action also combines the ingredients effectively, ensuring that flavors from the tequila, lime juice, and orange liqueur meld together beautifully.

Straining the mixture into the serving glass serves a dual purpose: it prevents ice shards from entering the glass and provides a smooth finish to the drink. Margaritas are typically served without ice in the glass, which is why the straining step is particularly important to maintain the drink's integrity and presentation.

In contrast, the other options do not align with the standard preparation for a Margarita. Simply mixing and serving or shaking and pouring over ice would not provide the right texture and flavor balance, while blending and serving is more associated with frozen variations rather than the traditional shaken Margarita.