What I do is I go in circles backwards around the enemy ship. it works a lot of the time. Also I found it useful to keep a long distance from them and have the cannoneers shoot at it first. You all have some good techniques though too.

Have your ship farther away so by the time the navy/EITC/undead ship can get sunk before it gets close enough to attack. Let the cannoneers cannon and when the ship is close enough to broadside, broadside them! :D

When I sail (except when I'm solo, of course) I tend to rely on my gunners to kill the ships, except when I'm in the positon for a broadside.

When turning i alwaysb use the Q or E button because they keep the turns quicker and tighter. Makes you be able to get off more broadsides when sailing alone.