If you haven't tried a group dungeon yet, or you did once or twice but it didn't work out, I'd like to offer some encouragement and a few suggestions. There are many players (like me) who come to ESO without much of an MMO background, so I offer what I've learned so far on this topic and invite others to do the same.

Reasons To Try Group Dungeons
1).They each have interesting stories that start in the normal (level 1-49) version and which are completed in the veteran (level 50) version.
2).They offer fun challenges.
3).Completion rewards a skill point and unlocks an achievement.
4).They raise your rank in the Undaunted skill line.
5).They offer unique drops.

Tricks to Find a Group
Finding a pick-up group is accomplished three ways:
1) Putting out a call ("LFG Fungal Grotto", that is "Looking For Group for Fungal Grotto") in zone chat.
2) Responding to such a call put out by someone else.
3) Using the Group Finder tool.

Playing a Group Dungeon
For combat:
Block. Even if you aren't a tank, don't forget you can mitigate damage by blocking at key times, especially when you can't move out of the way of an attack or interrupt it.

Dodge. Even if you are a tank, you don't have to stand in every red cone and circle. You can move while blocking or even double-tap for a dodge roll.

Interrupt. Everyone needs to do this. Keep and eye out for bow users and spellcasters. Interrupting them when they are powering up for special attacks can reduce the damage you or other players have to deal with and disorient the attacker, opening the way for a knockdown and possibly making them more vulnerable to extra damage based on class and weapon abilities (passive and active).

Self-Heal. Don't put everything on the healer. It's a group effort, after all.

Eliminate adds. "Adds", or "add-ons", are the weaker mobs that are close to/summoned by bosses. Sometimes there will be an explicit group strategy for certain players to focus on eliminating the adds quickly, but even if there isn't one leaving them in play increases the distractions you face while dealing with the boss as well as the damage the group takes in the fight. There may be some exceptions to the "adds" first rule, but when in doubt take them out.

These tips may seem obvious to some people but when you are new to the game or to the pace of group dungeons it's easy to forget or neglect such things.

For group interaction:
Be patient. With yourself and others in your group. Group dungeons are meant to be difficult, and there is a learning curve. You won't be able to beat every fight in every dungeon on the first try, especially if you are playing with a pick-up group that hasn't fought together before.

Be considerate. The people you play with will have different levels of experience and skill with this type of game. They may not understand what to do in certain situations. I am betting they would appreciate some friendly, non-judgmental pointers.

Be receptive. On the other side of that exchange, if someone is trying to offer you helpful suggestions, don't automatically become defensive. Everyone is learning the game, and even the best players get tips or insights from others when they are trying new content.