Alexander Hexforge posted a link in the comments to a guide that kezrik had set up over on Pirate 101 Central, an official fan site for Pirate 101. Thanks for the link, Alexander! I found it most enlightening!
Here are the broad strokes of what's posted over there:
Throughout the course of the game, through leveling and the Prospector Zeke side quests, you will be able to obtain 20 Practice points to spend on abilities from other classes. At that link, kezrik has shown the sequences which you have to use to get each type of ability. It's a great guide and very useful.
For my Buccaneer, I think I have chosen the right path. I will continue to go down the Witchdoctor path and collect all of the +power effects and +resist talents. Juju is one of the best buffs I've seen in the game so far as it boosts each characters main damage type all at once, so if you have 1 str based, 1 agi based and 1 will based, one buff will raise each member's main trait. What a time saver! After I have gotten everything out of the Witchdoctor class, I'll have to chose between using the remaining points for dodge in the swashbuckler tree or getting the healing from Privateer. Likely, I'll go with dodge so that my focus remains damage output, mitigation and avoidance instead of throwing healing in there. Although, if the +Power effects also affect healing, that might not be a bad idea to double up there.
Well, I still have some time to figure it all out!