Magic Items. If you received a permanent magic item during the adventure, increase your magic item count by one.
(ALPG 7.0 p. 3)
Downtime: Trading Magic Items. Magic items can't be given away to another character, but characters can trade permanent magic items received in play with one another on a one-for-one basis. Each party to the trade must spend 15 downtime days to trade the item. If you’re trading with another character playing in the same adventure as you, the downtime cost is waived. Consumable magic items (scrolls, potions, and magical ammunition) can’t be traded.
Upon completing the trade, you must create an entry on your log sheet indicating who they traded with (and their DCI number if they have one), the item traded away, and the item received in exchange. Information regarding where the item was located: adventure name, encounter, table number, roll, etc., should be recorded as well.
Permanent magic items are traded for other items of like rarity (i.e. uncommon for uncommon, rare for rare, etc.) on a one-for-one basis. The DMG or other official, published D&D products, are considered to be the definitive resource in determining the item’s rarity. Items without a specified rarity are unique, and can’t be traded. Items without any uses remaining also can’t be traded unless the item retains some permanent magical ability.
While a certificate isn’t required to facilitate this trade, if the item bears a certificate, it must accompany the trade or destroyed.
(ALPG 7.0 p. 4)
Permanent magic items are any magic items that aren’t consumable magic items.
With a few specific exceptions, these items all permanently count against your permanent magic item count. The number of permanent magic items your character possesses could potentially be considered when determining whether or not you are awarded an item found in an adventure.
Any permanent magic item awarded during play increases your permanent magic item count. Some items can be lost, destroyed, or simple wear out, however. Whether or not the item continues to count against your permanent magic item count depends on the item and how you come to lose it.
(ALFAQ 7.0 p. 8)
Permanent Magic Items. Permanent magic items are distributed at the conclusion of a session, episode, or adventure. A player notes the item obtained by recording it on their logsheet. Permanent magic items have specific rules for distribution to promote equity. Each character’s logsheet contains a column to record permanent magic items for ease of reference. Follow these steps to determine how to distribute permanent magic items. A permanent magic item can only be awarded if it, or the random magic item table it’s rolled from, is mentioned in the encounter in which it is found.
- If all the players at the table agree on who takes possession of a permanent magic item, that character gets the item.
- In the event that one or more characters indicate an interest in the item, the character who possesses the fewest permanent magic items gets the item.
- If the interested players have the same number of permanent magic items on the characters they played during that session, the item’s owner is determined randomly by the DM—usually by rolling a die.
(ALDMG v7.0 p. 4)
An item can be attuned to only one creature at a time, and a creature can be attuned to no more than three magic items at a time. Any attempt to attune to a fourth item fails; the creature must end its attunement to an item first. Additionally, a creature can’t attune to more than one copy of an item. For example, a creature can’t attune to more than one ring of protection at a time.
(DMG p. 138)
Also see http://dndadventurersleague.org/faqs/magic-items-faq/