Even a fellowship of two players is eligible to trigger Maneuvers, but since the power level of a Maneuver is dependant on the length and complexity of the sequence, the more members of a fellowship (up to 6 players), the more powerful their successful Maneuvers will be.
There are several ways for Fellowship Maneuver opportunities to arise during a battle:
Basic Combat
When you are fighting against a monster rated as Elite or higher, there is a chance with each damaging combat attack that you may push the monster into a state that will allow you and your fellowship to perform a Fellowship Maneuver on the monster.
Burglar Skills
Exploit Opening - When you reach level 12 as a Burglar, you can train this active skill that stuns your target and creating an opportunity to use Fellowship skills if you are in a Fellowship.
Trip - At level 28 another active skill allows you to knock an enemy down, opening up an opportunity to use Fellowship. Trip can only be used while in Stealth.
Exposed Throat - Is not a skill but a trait. After using your Double-edged Strike, you make an attack which inflicts high damage, with a chance of creating an opportunity to use Fellowship Skills if you are in a Fellowship.
Burglar Skills Item
Marbles - With marbles you can knock an enemy down or throw a creature off balance, opening up an opportunity to use Fellowship Skills. If you want to use marbles, train the passive skill "Clever Devices" at level 20. With this skill burglars can use devices such as caltrops, marbles, and stun dust.