Is it standard procedure to unlatch the cockpit door before an emergency landing in a small aircraft?
As always check your POH for procedures, however most light aircraft call for unlatching the door in the event of an emergency landing or ditching.  Two principle reasons: 1. It aids egress, which can be difficult with a jammed door. 2. It allows better energy absorption of the front part of the fuselage, by permitting it to crumple better.