There are two ways to play competitive 3v3: Solo standard or the usual 3v3.
Solo standard only groups solo players into two teams of three. It's usually the least popular competitive playlist in the game. Most people jump right into the usual 3v3 that allows players within a party. But Solo standard is a good way to meet fellow Rocket League compatriots and build your friends list.
If you have the friends to play with, it's better to play 3v3 with those friends because of the valuable communication that was mentioned in 2v2.
Even when you have an extra car on the field, don't send more than one person to the initial strike. Be sure to communicate so everyone is on the same page. 3v3 is the best place to use the aggressive face-off approach that was discussed in the 2v2 section. Send one person for the initial strike and lock up the ball in the center. Send the second teammate right on the tail of the first player to hit the dead ball on the opposing goal. This is a far less risky move in 3v3 because the third player has your goal guarded in case it doesn't work out like it's drawn up. That also means the success rate is lower, because the opposing team has someone in goal, too. Occasionally you can catch the other team off guard while the defenseman is grabbing boost.
Aggressive vs defensive
Like every other mode in Rocket League, there's an aggressive approach to 3v3 and a defensive approach. The aggressive approach fires on all cylinders. All three players are on offense at all times. This has its benefits, but rules have to be followed to pull it off.
In 3v3, it's all about team chemistry. That's true when it comes to players who are beginning all the way to the pro levels. Get comfortable with your two other players. Try out the two strategies. Stick with what works, and dump what doesn't.
It's all a process. Be patient through the losses, and working the process should lead to wins.
If you've been following along, they rely on the same basic rules of teamwork: Don't bunch, communicate and be ready for the pass.
One person should be in charge of centering the ball while the two teammates are ready for the one-timer. Passes to the center aren't always sure things. Usually they miss or are blocked before they even get in front of the goal. Having two players ready to take the shot is better than one. Another player is ready for backup if the initial shot misses. This can be a big help with rebounds off the post and crossbar.
The downside to an aggressive style of play is obvious. There's nobody getting your team's back on defense. Occasionally, a ball can fire off the wall and the opposing team takes an easy breakaway to the house.
Then there's the other side of the coin: defensive play. Only send two players on offense and keep one player as a designated defenseman.
This doesn't mean that you need to keep someone in goal the entire time. If someone is sitting in goal, that player is only a factor in 20-30 percent of the game. Instead, the defenseman can play up to about midfield.
The defenseman is there to keep the ball on offense. Just stay in line with the ball at around midfield when the two strikers are going to work on offense. When the ball gets close to midfield, knock it back toward the opposing goal. Drop back to goal if the other team gains control.
Be careful to not get too far away from the goal. If the ball flies over your head and into the goal, it's on you.
Know when to switch strategies
Adjust your strategy depending on how the game is going. Try an aggressive approach at first. If it's going well, stick with it. If you're getting crushed by runaway breakaways, drop one player back closer to the goal for defense. If you go up by one goal with a minute left, it may make sense to send someone to be a full-time goalie just to be safe.