A couple concepts that seem to be held sacred by many in the OSR include:
1. Low-level PCs are inexperienced bumpkins.
2. PCs are not heroes.
The perpetuation of these supposed "Old School RPG truisms" is getting old. I've been stewing about this for a long time. Let me finally chime in on the matter. This isn't going to be a huge diatribe. I suppose I just need to vent, and get my two cents out there, for all that they're worth.
Low-level PCs are Inexperience Bumpkins
Certain windy old pundits will tell you that low-level PCs are just up-jumped peasants. This idea has even taken concrete form in the Dungeon Crawl Classics RPG, with its 0-level characters. I don't care if this is how someone likes to play, but I take issue with those that hold this up as some sort of "gold standard" of old-school play.
I would argue that low-level PCs in D&D-related games, especially 1st-level PCs, have already been through some trials that push them beyond the pale of normal folk. I believe that this was the intention behind every iteration of D&D, back to the LBBs.
Look at the B/X level titles. Take, for example, the fact that in B/X the first level fighter is called a "veteran." OK, veteran implies he's seen some combat, right? Even level titles like acolyte, medium, and apprentice (cleric, magic -user, and thief respectively) don't necessarily indicate the lowest possible level of those professions. To be accepted into a religious order or a guild, doesn't one usually have to be somewhat accomplished in their chosen profession to be chosen in the first place?
So when a player portrays a 1st-level character as one jaded by harsh experience, that's just as valid as a player who wants their 1st-level character to be a wide-eyed innocent.
These low-level PCs may be inexperienced in terms of game mechanics, but that shouldn't have to equate to players acting out characters as totally inexperienced within their chosen professions/ classes.
PCs are Not Heroes
The windy old pundits will also tell you that PCs are not heroes. I think what most OSR folks mean is that PCs are not SUPERheroes, as portrayed mechanically in later iterations of D&D (especially 4E).
What is a hero, really? An evil person can be a hero to individuals of the same persuasion, no? Look at the DCC RPG. For each alignment, a cleric turns whatever is "unholy" to his/her alignment.
And the moniker of "hero" is more often than not foisted onto a person without their agreement/consent. Indeed, a true hero is someone who denies the fact of said heroism. This denial can come from true humility or one's refusal to be labeled by a society with which they take issue.
I find it interesting that there are still those that will try to tell you the game is just about being "looters." If you read the forward to Moldvay Basic, he holds up the (albeit cliched) example of the adventurer (dare I say hero?) slaying a dragon and saving a maiden. Does that sound like someone who thinks a game is just about killing things and taking their stuff?
But playing a stereotypical hero shouldn't be the default way to play any more than being a glorified tomb robber. Play what you want to play, and let the DM sort it out!
Again, you can play your character any way you want. If you want your old-school character to be a traditional lawful hero, go for it. If you want to be a brooding anti-hero, do it. If you want to be an amoral sort, do it. But just don't let someone tell you that you can't be a hero. Be whatever you define as being a hero.
Look, if there are those that want new characters to be those unheroic peasants at low levels, I say play on. Just don't hold that up to the rest of us as the "one true way." That's utter garbage.