Choose a loot distribution system and follow it.
Some popular loot distribution systems are:
DGKP or EPGP: basically a number of points are awarded for showing up to raids, which can be used to bid on gear. There may be resets going into new content or attrition on unused points.
Checkout an addon like Classic Loot Manager for help with this loot style.
Soft Reserve: Prior to starting the raid, people are allowed to soft-reserve a number of items (often 2, but you can set the number). If an item drops that people have soft reserves on, only the people who have soft reserves on that item are allowed to roll for it.
If an item drops that nobody has soft reserved, then it is up to you how to handle that. Typically, this will be MS > OS, or something free rolls.
Checkout softres.it which is a great tool for Soft Reserve management. You can also use the addon SoftRes which supports imports from SoftRes.it.
MS > OS: People roll for items that have dropped. Those who are rolling for their main spec have priority over those who are rolling for off-spec.
Loot Council: Someone from the guild, or a group of people (oftentimes a rotation group) votes to determine who should get items, usually with the intention of providing items for the greater good of the raid group.
Check out the RCLootCouncil addon for managing a Loot Council.
GDKP: People bid for items with gold. At the end of the raid, the gold received through bids is divided up among the participants. There are several rules that can be applied to this type of raid, such as minimum bids, or increments, etc. minimum performance requirements to receive a cut, organizer cut, bonuses for best DPS, healing or tanking, etc.
Onslaught Loot System: Raiders assign a value to each piece of gear they want within a raid tier, which is compiled into a spreadsheet, and used to determine which player gets an item when it drops.
Checkout the Onslaught guild website, or Aggro guild for a detailed explanation.
Personal Opinions about Loot Systems:
The Onslaught Loot System or DKP minimize potential drama but do require some set up and administration overhead.
Loot council is quite easy to set up, but requires people to vote, and can most easily lead to drama, if someone feels they are not getting the loot they want.
MS > OS is fairly easy to set up and minimizes drama, but it discourages a fully geared player from participating in their main spec.
Soft Reserve allows for off-spec rolls to be equal to main-spec rolls.
GDKP may be be controversial. Some maintain that it promotes RMT.
Whichever style of loot distribution you decide to go with, try clarify the rules beforehand so everyone knows what they are signing up for!
If you don’t already have it, you can set up raid-helper.dev on your Discord server to have people sign up with their class and spec for scheduled raids.
Best of luck! 