Many quests can be finished more quickly and safely with the help of a good group. Groups allow you to go places that you would otherwise not be able to go (and survive) by yourself.

Looking for Group Interface
The Looking For Group interface provides the best method for finding other players. Depending on your selection, either the "Looking for Group" or the "Looking for More" interface can be used. Both interfaces have tabs at the bottom that let you easily switch between the two. The Looking for Group interface allows individual players to be added to a queue of other eligible players looking for a group and matches them up based on preferences they have set. The Looking for More option allows for a group to search out additional members to complete a group.

Ask For Groups in Popular Areas
Sometimes it's good to start asking for a group in areas where players hang out. Main cities such as Stormwind are a good place to ask.

Guilds
Guilds are a great source of help. You should consider joining a guild because you might have an easier time getting help and finding groups. This of course depends on the quality of the guild you join. If it doesn't work out, leave the guild and find another one!

Meet Up On Site
Sometimes after traveling to a quest location you might find players already there. Ask them if they want to team up. For collection quests (collect x skins) people might not want to team, but for other quests, people will often like help. Give it a try. If you have two parties, see if you can merge the parties into one group!