Slime has many buffers, and sometimes it’s not easy navigating between them, slime-selector simplifies this task.
It’s not bound to any key by default, I bind it globally to C-z

(global-set-key "\C-z" 'slime-selector)

Then it allows you to select a buffer by a letter.
Some of the most useful shortcuts are listed here, the full list can be seen by pressing “?”.

• r   Current active REPL
• l    Most recently visited lisp file
• d   Debugger 
• c   List of implementations slime is connected to
• t   Threads list
• i   *inferior-lisp* buffer
• s    *slime-scratch* buffer (for writing one-off code)
• v   Log of slime events (useful for debugging Slime problems)