In GWX 1.02 I always went to assigned grid first. Depending on where I would end up, I would choose logical sealanes or convoy routes. The approaches to Gib have been rich hunting grounds for me. Also the convoy routes from Freetown going north, where I could keep on attacking night after night 'til out of torpedoes.
Now, in GWX 1,03 on first patrol with type VII based in Willi 1939. Things are quite different with this patch!