Cut: Select the text or file, then press Command + X
Copy: Select the text or file, then press Command + C
Paste (if needed after cutting/copying): Place the cursor, then press Command + V
Cut using menu: Select the text or file, then choose Edit > Cut
Copy using menu: Select the text or file, then choose Edit > Copy
Paste using menu (if needed): Choose Edit > Paste
Copy selected text in many apps: Highlight the text, then press Command + C
Copy files/folders in Finder: Select items, then press Command + C