Which level are you on? Here's how I do it...
I'm on my second game only (2nd level), but I think I got the hang of it now.
In my first game (English, Medicine), I retired at the age of 35 with fair health (as Mayor), all pirates defeated, all family members rescued, had my revenge, one lost city found, all promotions, and 6 secret treasure dug up, all special items, all specialists, about 98 or so fame. Isn't full mark in wealth because I was too loyal - I wasn't pludering enough. I kept using a Royal Sloop for the whole game, with one or two galleons along to carry some loot. The crew in early game is happy to content, but later on they're usually unhappy. I divided the plunder three times. I haven't dance - only once in the game, and I failed. So I decided my pirate doesn't want a nagging wife/girl friend to annoy him and refused all dancing

Late in the game I found Henry (the top pirate) and seized his large frigate - and I found it is a very nice ship... could be better overall than the sloop class.
The biggest problem I found in my first game is that the wind is always blowing from the East - and I travelled for quite a long period of time against it, and along the way there's little cities or ship to get action.
So in my current game, I started as French (same area as English), and sail in the nearby area to get myself a Frigate as quick as possible (for the max. crew, cargo and fire power over sloop). Then I choose Spain as my first target, and headed a little SE, attacking every Spain fleet I saw. I quickly gathered about 200 men and started sacking every Spain cities as well, along the way SE and then West.
I didn't keep most ships - they thin my crew on my flag ship, and slow down my fleet speed on the world map. I at most keep only two ships, if I know the goods have a really nice price nearby.
Surprisingly, as I follow that route, all the treasure maps, pirate hideouts seem to be quite neary by to my path - I don't even need to turn back at all. I just keep going SE then West, sinking ships and sacking Spain cities. At this time my crew grow to about 300 men at all times, and they are from happy to very happy.
I turn over cities to the other three nations to earn their favor as well as for a friendly port nearby for trade and repairs. Now I have almost reached the west-end of the sea - a few 500 soldier Spain cities I can't attack with confidence yet, so I'll stay there for a while. After that, I expected to be Duke (now Count) of England, and will sail north for those pirates, then east to English cities (morale should drop a bit by that time for the lack of action). Then I'll change my target to England and turn over cities to Spain... rinse and repeat.