Source: MMOWTS
Diablo 4 has rich content to tell its story. Players can enjoy a lot of time traveling through the game and exploring the secrets of Sanctuary. There is also extensive endgame content for players when they have completed the game's main quest line.
If you want to enjoy the game more, you need to level up your character to be stronger. I will tell you about some effective ways to level up quickly.
How to Level Up Fast?
Well, if you want to get more XP to level up, you will need to play more efficiently. You should focus on completing the campaign. You may have reached level 40 or higher when it's done. To get more XP, you'd better run the campaign at World Tier 2, which will increase the XP you can get from killing enemies by 20%, and World Tier 3 will increase to 100%, a really high bonus.
When the campaign ends, you should focus on completing dungeons and world events, finding Altars of Lilith, and leveling up your Renown system, which will give you XP when you level up a region's Renown.
Dungeons
Dungeons in the game are helpful to you. These dungeons not only provide you with weapons, armor, etc. but also provide you with a lot of XP to level up. These rewards will also help you play the game more smoothly. Dungeons can be reset, so you can challenge them again and again and get rewards every time.
There are Nightmare Dungeons in Diablo 4. Nightmare Dungeons are more difficult than normal dungeons in the game, and accordingly, the rewards will be higher. To unlock Nightmare Dungeons, you need to complete the campaign, level up to level 50, unlock World Tier 3, which is Nightmare difficulty, and unlock Tree of Whispers and Grim Favors. Then you may get Nightmare Sigils from Tree of Whispers caches' drop. It should be easy to get more when you have your first Nightmare Sigils because they are common drops in Nightmare Dungeons.
Different Nightmare Sigils correspond to different Nightmare Dungeons. Right-click Nightmare Sigils you want to use in your inventory to start a Nightmare Dungeon, and the dungeon will be signed on the map. There is only one active Nightmare Dungeon at a time when you use Nightmare Sigil. Nightmare Dungeon will be replaced by a new one if you use a new Nightmare Sigil again.
Nightmare Dungeons are not easy to challenge, be careful.
World Events
Apart from dungeons, completing world events is also a great way to get XP to level up. While world events can't give you as much XP as dungeons, they can offer Murmuring Obols, a new currency in Diablo 4, a bit like Blood Shards in Diablo 3.
Murmuring Obols can provide you with more Diablo 4 Gold. You can get Whispering Keys to unlock chests on the world map or get weapons, armor, and accessories from Purveyor of Curiosity with Murmuring Obols.
You can only bring up to 500 Murmuring Obols at a time before you increase the amount you can bring by increasing Renown in each region in the game. Some Altars of Lilith can also increase it. Do not forget to spend them if you haven't increased the amount yet.
World events are represented on the map by red-orange circles. It will be a bit of a hassle for you to complete an event because world events often require you to complete tasks in different places. It is worth it. You will get a lot of XP to level up.
Play on Multiplayer
Grouping up with other players will increase your XP gain in Diablo 4. You can group up to four players and get a 10% increase in XP gain. Not only that, you can get a 5% increase when you are close to another player in the game, not even in your group. It makes you level up fast.
Anyway, there are many ways to get more XP in the game. It depends on how much effort you want to make.