The following is a guide for ranking (something I seriously despise, when it is going too slow). I have stripped the newbie guide a bit to only add really -easy- places to rank. This is pretty much my ranking routine for most of my lowbies.
The lizards and imps in the Heroes School are the best way to get to lvl 6.
The lizards in the Lizard Caves near the Krilin Fortress are easy to kill, so are the horned lizards in the Jasa Lake east-south of Var Bandor, and will get you to level 9 quickly enough.
The young srryn in Jasa lake are outstanding experience. If possible, find a way to get a harlequin charmie from the Clockwork Mansion to aid you in fighting them (You would need a flight potion (available in most cities) and some way to get through locked doors (translucent potions from Kor Thrandir, for example)).
After completing the clockwork mansion quests (which gets you a clockwork hound charmie), or buying a wooden statue, you have a group of 3 (Yourself, a harlequin, and an additional charmie). With this group, and perhaps the Djinn Blade (Clockwork Mansion) or the spells you possess if you are a magic class, you can fight the worms in the Chaja Caves.
You might consider, from here, going to the Chaja Caves to fight chaja/miners or hunters. After that, you can head out to the forest of Morn to fight spiders of various sizes. After that, you can try the hill giants.
It is quite possible, depending on class and equipment, to solo rank on the Arien Way patrons (Kajal, et al) at this level. The Arien Way is a tavern just east and north of the west gates of Earendam. Be wary as it near the border between two oft-traveled areas, so it is quite easy to be ambushed while ranking. Also note that some characters may take offense to killing sentient races and that Kajal is good-aligned.
The Ambassadors in Kor Thrandir become interesting ranking mobs now. Exploit their racial weakness, and get around 700xp per kill solo.