A revelation has occured to me
Naval Battles are a bit neglected in the forums, as many people cannot/do not want to play them, as they don't understand the rules of conduct and are very often thrashed by the AI. Common 'solutions' are always-autoresolve policies and/or always attacking enemies with needlessly large fleets.
However, I have suddenly thought of a simple piece of advice which, so far (when I've tried it) has done wonders for my skills at sea:
Think of them as Land Battles
The Ships of the Line and larger 'Rate' ships are your line
The Bomb Ketches and Rocket Ships are your artillery
The smaller 'rate' ships are your light cavalry
The steamships are your heavy cavalry
Think of the side of the map the wind is entering from (i.e. with a west-blowing wind, think of the east edge of the map) as the high ground, the most important part of the field. Try to keep that edge in your control
Match your line up against theirs and engage, but move up your 'artillery' behind the line or to the side and bombard them
Send your smaller rate ships (light cav) to go do whatever you do with them on land, i.e. send them to the 'high ground', go round the back of the enemy line and harass, and chase down/cut off fleeing/isolated units (ships)
Send your steamships against the wind. This manoverability (they are not affected by wind direction) allows them to use the 'field' (ocean) in ways other ships cannot. Use them to harass enemy weak points and attack the enemy from areas they do not expect (the areas that go against the wind)
Now, as for tactics, I cannot suggest anything, but now that you think of the field as a Land Battle, all of your manouvering tactics on Land translate quite well. Obviously camping on the 'hill' won't work as well at sea, but other than that, it has done me wonders!