The next attack roll made against a target hit by Guiding Bolt (before the beginning of the caster's next turn) has advantage.Attack rolls against him/her are made at a disadvantage. The target of Foresight has advantage on attack rolls, ability checks, and saving throws.Attacks rolls against targets affected by Faerie Fire are made with advantage if the attacker can see them.Wisdom saving throws against ill effects of Dream are made at a disadvantage if the caster has a portion of the target's body.The targets of Charm Person, Dominate Person, and Dominate Monster do their Wisdom saving throws with advantage if you and/or someone friendly to you is fighting them.Blur causes creatures to have disadvantage on attack rolls against you (if they rely on sight).Beacon of Hope causes targets to have advantage on Wisdom saving throws and death saving throws.Ranged attacks against targets within normal range can be made, but with disadvantage on attack rolls. When making a melee weapon attack underwater, a creature that doesn't have a swimming speed (either natural or granted by magic) has disadvantage on the attack roll unless the weapon is a dagger, javelin, shortsword, spear, or trident.In a lightly obscured area, Wisdom (Perception) checks that rely on sight are made at a disadvantage.Ranged attacks in close combat (within 5 feet of a hostile creature who can see you and isn't incapacitated) have a disadvantage on the attack roll.Ranged attacks whose target is within a weapon's long range (but not within normal range) have a disadvantage on the attack roll.

Conversely, attacking an enemy you can't see has you making them with disadvantage.

Attacking an enemy while hidden (if they don't detect you approaching) or otherwise unseen grants you advantage on attack rolls.

Alternatively, it can provide advantage on the first of an ally's attack rolls against a monster.

Using the Help action during combat can give an ally advantage in one of his/her own ability checks before the start of your next turn (see 'working together').Dexterity saving throws are made with advantage. Using the Dodge action during combat has any attack roll against you made at a disadvantage until the start of your next turn (if you can see the attacker).Saddles on a mount give advantage on any check to remain mounted.When another character helps you use a ram to break a door, you gain advantage on the Strength check.A magnifying glass grants advantage on any ability check to appraise or inspect a small or detailed item.Using a crowbar grants advantage to Strength checks when it can be applied as leverage.Drinking an antitoxin gives advantage on saving throws against poison for 1 hour.Lances attack at a disadvantage when the target is within 5 feet of you.Small creatures have disadvantage on attack rolls with heavy weapons.Wearing some armors causes disadvantage on Dexterity (Stealth) checks.Wearing an armor you are not proficient with causes disadvantage on any ability check, saving throw or attack roll that involves Strength or Dexterity (plus you can't cast spells).Thief rogues of level 9+ have advantage on Dexterity (Stealth) checks if they move at no more than half their speed that turn.Rogues of level 18+ negate the advantage of any attack against them as long as they are not incapacitated.Figthters' protection stance can use a reaction to give disadvantage to an attack made against a creature less than 5 feet away.Stout halflings have advantage on saving throws against poison.Halflings have advantage on saving throws against being frightened.Elves have advantage on saving throws against being charmed.Dwarves have advantage on saving throws against poison.Because basic rules don't include a dedicated list (understandable, as it's usually a side effect of a very wide variety of actions or situations) I wrote a summary with the information from the different instances where advantage or disadvantage are mentioned in the basic rules, just in case anyone else is curious. In another topic someone was wondering about the new advantage/disadvantage mechanic, and under which situations it comes into effect. Summary of situations causing advantage or disadvantage.

D&d 5e turn