This is my explanation of how leveling up works in D&D 5e. It’s not meant to add anything new to the conversation; it’s simply a distilled version of the original rules, with some clarifications that I found helpful. Most of this comes from the Player’s Handbook (and the corresponding roll20 page).

This post will hopefully continue to evolve. At the time of writing, I’m a new DM (and an inexperienced player, at that) so comments and corrections are always appreciated!

Increase Your Ability Scores and Proficiency Bonus

Your ability scores and proficiency bonus increase every few levels. Ability scores are class-specific—look in your class description. For example, from the Paladin page on roll20:

When you reach 4th level, and again at 8th, 12th, 16th, and 19th level, you can increase one ability score of your choice by 2, or you can increase two Ability Scores of your choice by 1. As normal, you can’t increase an ability score above 20 using thsis feature.

Proficiency bonus is not class-specific, but can be found in the ever-handy class table. It is also present in other places, such as the general “Character Advancement” table shown on this page.

Increase Your Hit Point Maximum

Increasing your HP maximum is done in two steps:

  1. Add a new Hit Dice, and add the new Hit Dice’s value to your HP maximum.
  2. Add your constitution modifier.

Though this sounds easy, each step needs a little clarification.

Adding a new hit dice: For every level, you gain a new hit dice. I don’t know what hit dice actually do. I’m sure I’ll figure it out soon enough.

Keep Track of Additions and Changes to Your Class Features

I’m not sure what the right terminology is for what I’m calling “class features”. By “class features”, I’m referring to the list of abilities and features that appears after “Starting Equipment” and the class table on your class’s page. I’ve seen this term used in other places, so I’ll use it here.

These features generally unlock as you progress through your levels. Each time you level up, you should browse through these features again and see if you’ve unlocked any new features, or if any existing features have upgraded. An easy way to do this is to find your class’s page on an online or PDF copy of the 5e Player’s Handbook and use Ctrl+F to search for “level”. This should highlight all features which mention unlocks/advancements at specific levels.