The simplest and slowest way when you need to use something from the system clipboard:

Copying: Enter visual mode (v) Highlight the text I want to copy then enter in command mode "+y which basically means "Use a register for following command (") make it the external clipboard register (+) and yank/copy (y)"

Pasting Move to where I want to paste then enter in command mode "+p to paste after the current position or "+P to paste before the current position

If I don't need to copy/paste stuff to applications outside of vim, then I can skip the "+ register setting part, and just use the default internal register.