1. Get a low level player to invite you to a party (15 levels or lower).
2. Dungeon Helper Mode should apear on the party pictures providing the newbie is a low enough level.
3. Let the lower level enter the dungeon and you follow after he/she has entered.
If you meet the requirements to be a dungeon helper, when inside a dungeon every kill they or You make will Regenerate your
stamina on an average rate. Its best to choose dungeons with loads of mobs for a beter regen rate.
You will NOT recieve any EXP or loot above blue (Its rare but you can get other quality's above blue).
You can check how much your stamina Regens by pushing C.
If you have 0 stamina you will NOT be able to gain Exp from monsters, It also hinders your quality drops 99.99% of the time
you will not get loot above Blue quality (you can get above blue quality but its very rare).You can still enter dungeons
with 0 stamina to complete your quests, and you can still gain exp from the Quest reward
including Daily Quest Exp reward.
For the higher levels with 0 stamina wishing to enter a Relic Dungeon. The main Relic Boss will still drop those relic gems
and im pretty sure they still drop Tier 10 materials as well, how ever they will not drop set gear when you have 0 stamina.