I have been fortunate enough to be able to market a few of my builds through contract, and I generally estimate charges based on $5/hour, and try to reach a middle ground on the amount of detail wanted vs the amount of money available, BEFORE construction begins. This keeps the door open for more people, while at the same time, making the sky the limit to others!
I also do artwork, and for those who've asked me to "go all out" on their project, I included an Original painting of whatever subject it is I'm building. It would be the sole example of this art in existence, displayed alongside his custom built model. In one case, I was even able to secure a piece of the sheet metal from the aircraft the model represented, which was inside the display case itself, in shadow-box style. Things like this help add a touch of authenticity (a genuine value for thier money) to their display and they showed their appreciation well.
Advertise in the big (whatever subject) magazines (and websites), on real (and cyber) bulletin boards at special events, and other places where (whatever subject) owners will see them. I happen to be a firm believer in the printed media as still an effective means of marketing!
Maybe a decked-out example of your work and a stack of business cards on a table (or the hood of your car) at larger Airshows/Open House/Dedication, etc.... it would be a more direct approach at getting contract jobs. With experience, you'll learn what method of charge works best for you and your style, and your customers.
Word of mouth goes a loooong way in most circles of interest/enthusiast, as I'm sure you know, and you may soon have to curtail orders just to have a few minutes with your family each day!
Take care and best of luck!
Frank