5th edition is not alone among editions of D&D that do not have "level zero" rules. Level zero rules are not universally useful, but they can come in handy for some styles of game.
For instance, one day I will run a Connecticut Yankee in King Arthur's Court game (alternately, Narnia or Fillory), perhaps using modern New Yorkers transported into a fantasyland where they can gain D&D character class levels.
Another use for "zeroth level" is for the Dungeon Crawl Classics Funnel.
You can also run a "farmboy to hero" destined messiah type of game, with the PCs starting as shepherds and pig-boys and so forth.
I've seen some others' attempts at creating level zero rules, but they all added something. These are stark and simple and provide instructions for "leveling up" to first level. So here are the rules.
A 5th edition D&D 0th level character has:
- The core six attributes (Str, Dex, Con, Int, Wis, Cha) plus racial modifiers
- Maximum hit points: 6+Constitution Modifier
- No hit dice
- Armor Proficiency: None
- Weapon Proficiency: Proficiency with daggers, darts, slings, quarterstaffs, and light crossbows; plus anything your race bestows
- Saving Throw Proficiency: None
- Language, Tool, and Skill Proficiency: You start with the language, tool, and skill proficiency your background and race bestow
- Starting Equipment or Gold: You start with the equipment and money your background bestows
- Your Proficiency Bonus starts at +1*
(* this lets the few skills, tools, and weapons you have proficiency with actually matter)
Note that you do not get a weapon to start with. Level zero characters are torchbearers, deckhands, and pig farmers. They're not walking around armed like adventurers. You'll have some money to buy a weapon, though. Each background provides enough coin for anything you're proficient with except the light crossbow. Some backgrounds provide tool proficiency and tools that would let you make a weapon, if you have time. Note that some backgrounds also provide a weapon (a Soldier can have a small trophy from a fallen enemy, like a dagger).
Gaining your First Level
You improve to level 1 once you've had training in a character class. Usually there's some danger and adventure you have to go through before you can get that training, though. That's the whole point of "level zero"!
At level 1, you select a character class and...
- Replace your maximum hit points and hit dice with the ones you gain from your class.
- Gain the Armor, Weapon, Skill, Tool, and Saving Throw proficiencies your class bestows.
- Gain all the class features associated with your new character class.
- Gain your choices from the standard equipment your character class starts with at the DM's discretion. These are given to you or earned during your training.
- Improve your Proficiency Bonus to +2
That's it. Easy as pie!