Updated June 11th, 2019.
You can search for someone in your Mac’s Contacts app (“Address Book” app on older systems) by typing the first initial, then a space, then the last name (or enough of the last name for the Mac to find what you’re looking for). It also works to type part of the first name, then a space, then the last initial. Basically, you type a little bit of the first name, and a space, and a little bit of the last name, and as you type the Contacts app narrows things down.
For example, if you’re trying to find ME in your Contacts app, you’d do ⌘-F to put the cursor into the Find… box, and then you’d type “c boyce.” You don’t have to hit Return– the search is “live.” You could even type “chr boy” and it would work.
Today is my sister’s birthday, by the way.