Anytime you are outside of a text input field, press Alt (Windows) or Option (Mac) ahead of the following letters to perform the corresponding action.
Alt + C for a new Contact
Alt + E for a new Email
Alt + N for a new Note
Alt + W for a new Work
Alt + S to open Global Search
After composing an email:
⌘ + Enter (Mac) / Ctrl + Enter (Windows) to send