* Best place to start, if you're a total newbie:
Valkyre (Newbatia), and go up to the Newbie College. DO read the signs; they aren't just for decoration. Many things are common to tons of worlds, but not all.
Other areas for lowbies in VK:
Chessboard (some knights assist or attack, get a map because those invisible walls can be ugly) - nice eq too. Even better if you're not a thief, I stabbed myself dead a couple times

Little mobs in town/guilds
Fens (south of town and then head west, past the entrance to the circus) - not much eq.
* Thordfalan/Bal Harbor:
has the problem of being full of Big People, some of whom confuse newbies with pebbles.
Lowbie areas:
Kobolds (west of town and take the first south)
Park (east of town and take the first north)
Little mobs in town
Sewers
Goblin Mountain (east of town and go straight until you start seeing goblins)
Some mobs fight each other in/around town; sometimes you can find mortally wounded mobs caused by one of those fights. Be careful not to kill other people's kills, though!
* Thule/Aisholm:
has the problem of never finding anybody to group with and few newbie areas; less rudeness problems than BH
Penguins (north and take the first west) are easy and have some nice eq; the other penguins (south, to the beach, be careful to avoid underwater rooms) are also easy but sometimes you run into token-hunters there, who can be very rude.
Little mobs in town.
*Niebelung/Settlestone:
Don't even think of killing anything in town. Either it will be bigger than it looks, or it will get assisted, or... just not worth it.
Grymlyns are the easiest area. The old grymlyn at the well is harder than he looks. This area is west of town, head south after the ticket seller.
The beach also has many small mobs. Remember to use con, be careful with underwater rooms.
Fairy forest is next. Careful with the squirrels of doom. Fairy tree is right at the forest.
I usually start in either AH or SS (for tranquility in the first few levels and eq) and then move to VK or BH (better leveling once I'm dressed up), but that's me: like I said before, the best place for a true newbie is VK.