Ah, gotcha.
On the official forums for each profession, if you search "leveling build" you can usually find a thread. They often sit back on page two or three, since people, as you pointed out, are most often interested in discussing endgame builds.
For Warrior, I've just been doing the 4 signet thing with Deep Strike (ten points in arms, +precision for each unused signet). Apparently it's been nerfed at some point, but I still have a ridiculously high crit chance, at least in the lower levels. Axe/Mace to chop through things and build Adrenaline fast.
It's been a long time since I leveled my Mesmer, but I leveled her all the way without help from crafting. At the time, Illusionist's Celerity was the must have skill, but then it was only a 10 point trait in Illusions, and they have since moved it to a grandmaster trait, for some reason. It makes a huge difference in how many illusions you can create. Linked to that, as soon as you can get reduced cooldown on the weapon you're using most, the better, as it also means faster illusion generation. Sharper Images in dueling was also a must-have trait at the time, as it signficantly increases your DPS because suddenly your clones can do damage by applying bleeding.
On Guardian (which I also leveled without crafting), Inspired Virtues, at 5 points in Virtues is also a must-have, since it grants boons every time you use a virtue, which is often.
On Engineer, my must-have was speedy kits, but that's just about getting around maps, not survivability.
On thief, I've got no idea. I died a lot, which is probably why mine still sits at level 63 at a crafting station in LA, leveling weaponcraft for my other characters. I had trouble getting even the so-called "immortal" or tanky builds people post for ezmode leveling to work. So much of the profession design is oriented around active defense, and Thief seems to be the epitome of that.
That's about it for what I've got on early traits for various professions.
Mostly, I just stay out of zones where I die a lot until I get leveled and/or geared up enough for them to be manageable.