I'm going to give you the same advice that I give any player who sits down to play with me in real time. It's this: don't worry about what powers or abilities the character classes have, just play the character that you want to play. You'll have more fun if you start with a personality and then build from there. Imagine a list of personality traits, maybe a background to go along with them, and then let that guide your selection of stats and class.
Keep in mind, also, that in OD&D more than any other edition, character class is more about what you "are" than what you "do". (3rd edition is unique among all the versions of D&D, in that class was very much something you "do", because it could change so easily and so frequently. In all other editions, even 4th, your class is much more your archetype, and you have to figure out how closely you want your own character to hew to the stereotypical member of your class.)
The demihuman classes are meant to be very stereotypical, in the vein of Tolkien. If you're an elf, you're a bloody elf: immortal, wise, deft, skilled at all arts (especially healing, woodcraft, and archery), with an inborn loathing for goblinkind.
Human classes, meanwhile, can encompass a wide variety of types. If your class is scholar, that still says relatively little about your character. Bookish professor? Country parson? Crusading paladin? Mysterious druid? Savage shaman? Monster-hunting Van Helsing wannabe? Fringe theorist, a la Daniel Jackson? Member of some kind of mystic templar order, like a Victorian Jedi Knight? Whatever you can come up with. I added skills to the game so that you could flesh that out and have a little bit of game-mechanical representation to back it up.