Secondary professions for a Ritualist

Ritualist/Warrior

 * The elite skill Spirit's Strength combined with a Warrior IAS such as Flurry can make a Ritualist melee attacker much more threatening. Be wary of the Ritualist's light armor however.

Ritualist/Ranger

 * The Ritualist's primary attribute, Spawning Power can be used to reinforce nature spirits.
 * Serpent's Quickness and Quickening Zephyr can reduce the lengthy recharge times of Binding Rituals without using an elite slot.
 * Skills like Dual Shot, Triple Shot, and Volley multiply the effect of Spirit's Strength.

Ritualist/Monk

 * Ritualists lack hex removal skills, and can benefit from the expanded condition removal from monk skills.
 * Attuned Was Songkai can be used to lower the cost of expensive spells that have quick recharge times for a great effect.

Ritualist/Necromancer

 * Spawning Power makes undead allies that have good survivability, but generally have less damage and lower armor due to the lack of Death runes.
 * Explosive Growth is a useful way to add damage when summoning minions, particularly with Animate Bone Minions.
 * Spirit's Gift is also good to use while summoning minions as it will help keep your team alive as well as your minions.
 * Boon of Creation assists greatly with energy management, as it affects minions as well.

Ritualist/Mesmer

 * Arcane Echo can be used to increase the damage potential of channeling builds and Ritualist farming with Vengeful Was Khanhei.
 * Mantra of Concentration or Mantra of Resolve can be used to protect against interruption.
 * Mesmers have several cheap anti-Hex skills, such as Revealed Hex, Hex Breaker and Inspired Hex.

Ritualist/Elementalist

 * Glyph of Lesser Energy is useful in reducing the cost of your more expensive spells.

Ritualist/Assassin

 * A player may not Shadow Step while holding an item. In this way a Ritualist can bomb targets by using a recall skill and forcing the item they are holding to automatically drop.
 * Daggers can strike more often than any other weapon in the game due to the Assassin's chance to double strike. For this reason, combining dagger attack combos with weapon spells and Spirit's Strength can cause a lot of damage.

Ritualist/Paragon

 * This profession combination provides little benefit for a Ritualist primary.

Ritualist/Dervish

 * The elite skill Spirit's Strength works well with scythe attacks due to the AoE effect of scythes.