A Proof General tip.
If you place the cursor after Proof. and type C-c C-return, you'll notice that the window displaying Coq's responses is (annoyingly) empty, instead of showing what is to be proved. The reason for this is that, actually, a different buffer is being displayed! (To see this, do C-c C-n and C-c C-u a few times and notice that the buffer name in the mode line changes.) You can use C-c C-p to switch the display back from the *response* buffer to the *goals* buffer.
Originally found here.