The person at the rudder often doesn't see what's happening because of the sails, and others need to be watching out for rocks and the like to avoid crashes and help keep you all alive. If you travel during the night, we'd also recommend extinguishing lanterns on the ship to make you harder to spot from afar. You are not alone in Rare's digital sea; there are also other nasty raiders sailing around. If (or perhaps rather "when") you see a boat nearby you can choose to take the battle to them, or wait or see what the others do. In most cases, the others have things to do for themselves and it won't be a big battle, but sometimes it'll be a fight until someone goes down.
Therefore, fire back, fire fast, and fire hard. The best place to hit is right at the water line because it quickly fills the opponents' boat with water. Thus, they have to set aside people to fix the boat and pour water while you and your crew can keep on with the bombardment of cannonballs into the enemies hull. If you spot a boat that's anchored somewhere, we can also recommend that you swim over and sneak aboard (it works on all ships but it's very difficult to catch up with a moving vessel), killing off a crew who probably won't even see you coming because they have a ship full of water, planks to nail, and cannons to shoot. It helps even more if your opponents aren't in a party, which is why we'd always recommend playing with friends.
Inside your boat is a weapons cabinet. It's in the cabin on the sloop and at the front of the bow on the lower deck of the galleon. You start your pirate trip with a sabre and a gun that you activate and switch between with the Y button, but those can be exchanged for a shotgun or a sniper rifle. They are all well balanced and cost nothing, so if you have a good sniper with you in your crew, arm them appropriately. The sabre should be kept because it never runs out of ammunition, but we prefer the shotgun instead of the default pistol as it does a great job when people try to board you, whenever you want to take over someone else's, or when we're surprised by skeleton soldiers. You can never have more than two weapons, so choose carefully. Unfortunately, your choice between games isn't saved, so if you find a favourite you'll have to select it every time you start anew.
Once you've found your island there'll either be a hidden chest (Gold Hoarders), animals to catch (Merchant Alliance), or a boss to kill (Order of Souls), and all that's left to do is perform your duty. The former and the latter are resolved when you find or kill the chests/bosses as directed, whereupon you will get a chest or a valuable skull to sell at any Outpost. However, catching wildlife is a little trickier because the animals need to be returned to the specific Outpost mentioned in your contract. Therefore, consider what you're hauling and where you're hauling it to.
It's best to do multiple assignments at once when you are out sailing, as it saves time, but if your ship gets sunk by other pirates, the risk is that you'll lose everything (or you'll end up marooned on a nearby island and with nothing but what you were able to carry). You simply have to measure up the risk and reward against each other. We tend to do two to three missions before our crew collect the goodies. Often you can find an extra chest or a box of expensive spices, and even bottles stuffed with mysterious maps, so it's worth keeping an eye out for things that can give you more treasure and chances for additional wealth.
Each time you complete a mission for a faction your reputation rises with them and, as you grow in stature, you also get more and more advanced assignments. Eventually, Gold Hoarder missions turn into really tough puzzles where you will follow clues, play music at tombs, or even shine your lantern in the right spot to find the treasure, while the battles can be almost overwhelmingly tough. Sea of Thieves is about cooperation and because you never really know what you'll face, it's also about communication. The day after launch, our team found a dozen chests that we hid on the balcony of our galleon. When we arrived at an outpost to sell it all we realised that another player had snuck onboard while we were anchored and was in the process of throwing our precious chests into the water, probably hoping to make us think they were long gone so they could sell them when we left.
By working diligently, things will go a lot better. If one person frequently checks the map and speaks tells the person at the rudder where to sail it becomes easier. The same thing if someone is looking for enemy ships and continually adjusts sails and helps when the anchor is to be lifted as more manpower makes it a lot faster. In stormy weather, this is extraordinarily important as water is filling up your ship and holes can spontaneously occur because of harsh conditions. Remove all the water with your bucket and repair, keep an eye out and communicate so you do not have to go to down because of the weather.
If you travel outside the borders of the world map, the water becomes blood red, ominous music plays and the ship begins to break and take in water. If this happens, a good trick is to pull the rudder in one direction and rapidly lower the anchor. This will initiate what can best be described as a handbrake turn as it lets the ship turn very quickly. Then you just have to fix the holes, grab your bucket and bail all the water out of the hold, and then quickly sail away! This trick is also good if you need to turn around quickly because of a collision or during a battle. Larger ships have superior firepower versus smaller ones, but the sloops are faster and more easily controlled. Releasing the anchor and simultaneously firing a broadside of four blazing cannons against a smaller ship can settle the entire battle in a heartbeat.
The anchor is of course also used when you make landfall. The most obvious thing is to park on the beach as it's convenient, but sometimes it can be a good idea for some of the crew jump off and swim to the shore, letting one player sail the ship around the island to either keep moving in case the need arises for a sharp exit, or to find themselves a place where it's harder to be detected. Leaving someone on the ship for a quick escape or to fix things up in case of a drive-by attack is also good if you want to make sure you actually have a boat left when you return with your treasures.
One last tip we want to offer is that you should protect the person who is carrying the treasure. That person is significantly slower and can't defend himself or herself. It makes them an easy victim for pirates, sharks, snakes, and skeletons. Also, we think everyone should help to carry chests from the ship when the goods are to be sold. If someone transports the, from the boat to the beach while another runs and sells them, you'll increase the chances of getting everything sold before pirates show up to ruin the fun. As soon as the treasures have been sold, the money is yours forever - or until you spend it on grog and a fancy new eyepatch.
With these beginner tips, you should quickly become a seasoned pirate who can defend themselves when required and find the most valuable treasures. Remember, nobody gets stronger, faster or anything like that in this game; there's no progression in that sense. Therefore your opponents might have more beautiful tankards than you, cooler hats, and even handsome figureheads on the boats - but they're just as strong as you. Thus, as a newcomer, you can fully defend yourself, the only difference is that you'll be doing it with less swagger. Other than that you're as much a pirate as anyone else. Good luck!
And another thing... if you go into settings>controller you can assign hotkeys to the d-pad. There are two open slots where you can map shortcuts for bananas and planks, for example. If you don't use the chat options you can even consider moving things around and utilising the two shortcuts already assigned for text chat and emotions, giving you up to four shortcuts. We'd recommend bananas, planks, and cannonballs, as they're the resources you'll use most often, and maybe use the fourth for the spyglass, as it's always useful having it to hand, as you never know what you're going to see off in the horizon.