Become a student of design or be ready to pay someone out the yin-yang to do it for you.
A hot date for me and my wife is going to Borders, buying a cup of coffee, and reading every home/building/renovating journal on the shelf. American Bungalow is my favorite by far… my wife and I often agree on design, and she’s been accused of having a ‘man’s taste in design’… meaning that she’s very well happy with large oak posts and heavy woodwork on fireplace mantles. (Geez, that sounds weird.)
Houzz.com is a tremendous resource as well. It’s like a giant photoshare for builders and renovators, and we’ve had great luck in blending styles from various builders and coming up with a few ideas all our own (I can spend way, way too much money on granite in places where most people wouldn’t think granite should go)
View other houses in your target area. I’ve wholesale ganked staging and design ideas from my competition, and I am absolutely not ashamed to admit it. If it is awesome and sells, I’m happy to steal it and use it myself.
I wish I could say that I have a single design, or set A-B-C that I use with every house. Sadly, I don’t. A lot of that has to do with the fact that I draw from much older design models than many renovators… the houses I work on are either older (1950’s) or designed to look older (Neo-bungalow/victorian crossovers).
All that means is that while I have certain design modes I try to follow (No horizontal tile surfaces, for example), the houses I work on generally each tend to require something unique to the house.
Example, the neo-bungalow we built most recently has a craftsman/early Victorian crossover trim package that incorporates both simple door and window casing with very craftsman-looking pediments, and cove molding which is a very early-Victorian thing to do. We did it that way because it emulates a specific style and era that we were trying to project in order to fit with the area (Which is dominated by 1920-1950 designs)
Another house, which is a post-war build Bungalow, we opted for baby-howe trim casing for the doors and windows… an ‘older’ look than you get with modern window casing, but very much in keeping with the style of the house.
I guess in terms of color palette, we tend towards the neutral. The walls are usually biscuit or some other variety of builder-beige, and the trim is either white or vanilla. I prefer light colored hardwood floors in small houses, and darker floors in larger houses. Often, though, the condition of the existing floor with dictate shade (Dark enough to cover all blemishes)
This is a really time consuming way to do things and I don’t recommend it unless you want to spend a lot of anguish worrying about every little detail of a rehab. If I wasn’t such a tightwad who was obsessed with design perfection I’d just hire a danged decorator to tell my crews what to do, then gnash my teeth in silence when it bothered the heck out of me but sold anyway.
(Don’t get me started on the sheer heck I put my floor plans through to ensure that they come out right…)