Star Trek Aliens Approach to Races- Elves are humans with pointy ears. Halflings are short humans. Dwarves are stout and tough humans. Orcs are brutish strong humans. It’s not a cantina filled with bizarre morphologies or strangeness. That’s for later suppliments (which includes even the races I really like, the warforged, the changeling, and critters from the XPH). Your party can and will include creatures of colorful races, but they’re basically just humans with funny ears. The rules will give you a basis, and you go from there. Your elves are different than mine. My dwarves are abstinent, serine Tibetan monks. Your halflings are dinosaur-riding nomads. Awesome! All we need to be able to do when someone mentions a “dwarf” or “halfling” is get a picture in our heads anyway. Everything else can be explained at the table or in the campaign setting.
Heroic Fantasy- D&D started as a descent into the wierd and wonderful with oldschool dungeons. That’s fine and dandy. Keep true to the idea that it takes place in a wierd and wonderful world and we’re all good.
Classes & Levels- I don’t much care for them, but they’re D&D. D&D is about the common point of everyone knowing what you mean when you say you’re playing a 10th level rogue.
Random Factors via Dice- Conflict resolution may have become more structured with the d20 System (a good thing, in my mind), but the random element of resolving a challenge will come from polyhedral dice.
A Dungeon Master At the Table- For all the talk about 3.Xe “emmasculating” the DM, it’s still the case that D&D is run by a Dungeon Master. Remove this figure and then we’ll consider whether or not it’s still D&D.
Monsters to Kill and Loot to Steal- You find monsters/monsters find you. You fight them. When they die, you take their stuff. “Looting the corpse” and “searching the bodies” are absolutely a part of D&D, even if I don’t particularly find them “heroic”.