Pirating includes both the land profession Highwayman, and the sea profession Pirate.
See all Professions
The best way to pirate is to get a very powerful vehicle, but also with a good speed. Since a pirate only gets income by stealing cargo, they need to take as few weapons as possible. Often, a pirate will watch a player who has a valuable item, and have a radar active. As soon as the player moves their item, the pirate checks the radar to see which route is most likely, and sends an interception force out.
Another strategy is to send a large force into either Trader's Tree or Pirate's Peak. On the way out, you target your targeted vehicles, Many traders consider these routes much safer, and thus bubble less efficiently. Many pirates make a killing doing this once in a while.
The greatest danger is that guards can fill their cargo entirely with weapons and not decrease their chance for profit. A guard with a good vehicle and a cargo loaded with weapons can be a major risk to a highwayman. Only pirate if you can afford to pay bribes.
On the sea, the system changes somewhat. Since ships can be destroyed in battle, there is a greater risk of using more valuable ones. Also, other pirates may be of even greater risk at sea. A major advantage at sea, however, is the growing fishing market, where the expensive fish are being transported in large quantities.
Also note that there are no major Bounty Hunters
It is quite unlikely a highwayman will make a lot of gold immediately. In fact, without a good understanding of vehicle combat, you will quite likely lose a lot of gold. It takes a lot of luck to hit a trader early on, and chances are that many traders use more expensive vehicles to transport valuable goods.