We were just a bunch of Eugene area people, most of whom attended or were Staff/Volunteers for Sakura con for years.
We decided that we needed a con in Oregon and "just did it." We asked friends from Sakura Con for help. Unfortunatly, the person who helped the most has now gone into the Navy (Isaac), but many of them were willing to give us information.
The best advice I can give you:
1. Have some members that have been staff members of another convention before actually trying to start something from scratch and start planning your event a year in advance.
2. (most important). Attend C cubed. It's a convention for people who put on conventions and it's held every year. This year it will be in Seattle in June. (It seems to rotate between Portland and Seattle each year).
I would highly suggest having people with that kind of experience because there are a lot of legal issues that come into play and you really need to be prepared for them. Also, the hotel community communicates. Let's say some group put on another Anime Con (not saying your group, but another random group) and this group pretty much tore the place up and had parties in the event rooms with underaged drinking...(blah, blah, blah...lots of bad stuff...). Word of this will get around to all of the hotels in the area and it will make it harder for other conventions associated with Anime to be able to book conventions (or they will require 5x the insurance as other kinds of events or any number of things that will make it very costly for the next people that come around).
Right now, as the first Portland Anime convention, Anime now has a good reputation (sigh of relief!). The hotel saw many of us as some sort of quirky people, but they also saw that we didn't distroy the place and we were well behaved. It's in everyone that loves Anime, Science Fiction, Gaming or any other thing like that's best interest to make sure us 'nerds' keep giving them a good impression. One of the fastest ways to ruin it for everyone would be to host an event without tons of research, planning and some experience.