Cleanest/Fastest way to avoid calling and retrieving data from the database multiple times?

So this may be a very noob question, but I believe if I can get the answer to this I can clean up code and speed things up significantly.

I build projects using Woocommerce quite a lot, and in doing so I find myself writing functions that often use the same calls from other functions. For example:

or

For example. Those are used quite often throughout various functions. What is the best practice (both for speed and cleanliness) to call these once and reuse them throughout my functions.php file – while still allowing me to call said function from a .php file and not receive errors? TIA.