Hire a couple of NPCs to beef up the party in the beginning. Later on you can kick them out when your main characters are strong enough.

Wandering monsters you meet on the roads can be brutal, so as a rule the less you travel the better in the beginning.

Personally, I love using a fighter with a reach weapon with improved trip + combat reflexes + whirlwind attack.
Also, remember that druids turn into good fighters at level six once they can wildshape into bears, and clerics turn into good fighters once they learn divine power at level 7; I highly recommend having one of each in your party.

Sorry to necro, but looks like I'll be trying to get back to this plan of mine after all. I think I've got a decent-ish handle on what I'm doing, but there is one thing that I'm iffy on; skills. Regarding social skills, for instance, is there any benefit to loading up only one member of the party with social skills, or should I spread them around and maybe have multiple characters use the same skill? I ask because it seems thus far that a lot of times dialogue will be initiated by an NPC to someone other than the party "face", meaning that if I had wanted to use a certain social skill, I was unable to do so. It hasn't posed a problem yet, but I'm wondering if it might down the road.