For me the problem I see far more than anything else is not a true lack of concern regarding flow. More than anything, it is overenthusiasm. When I got my first vehicle ('89 F150, lifted, dark blue/black two-tone) I knew about flow and style, but I thought I "knew" better than most people... I'll just leave it to your imagination what a 16-year old with an Autozone-only budget can do to a nice vehicle....
More than anything it becomes a learned technique or trade!
This day and age I have a unique challenge: I recently bought a RS 5.0 (gold rush!) xB with chrome rims already on it. Basically: chrome slapped onto a gold/black motif. Depending on what a person wants to go for, it can work, or it is a step in the wrong direction. Overall I am still trying to figure out what I want to do with an already modded xB (RS, remember?) and make it more my own and develop a better sense of flow to the vehicle.
What helps me most is to think about what you envision as the iconic driving situation for you, and let the cars' design unfold itself in your mind! For me, I think of two things, and they both have a common theme: nighttime. I envision myself cruising through a brightly lit downtown at night, and blasting along at 80+ mph on a desert highway. Now, what would work best in these two situations? I have two extremes: a large amount of nighttime lighting and none whatsoever! One area has a ton of lights reflecting off the vehicle, and the other just your interior lights and headlights..
For me, I like to take small steps. I am currently looking at getting a color-matched shark fin antennae, lower the rear 1-2 inches, powdercoat my rims gloss black, and painting the brake calipers gold. I want to move small and let the vehicle respond with each step, and slowly (and with much deliberation) let its' looks come forward.
More than anything: I advise people to HAVE PATIENCE! Money is scarce, and patience and deliberation will result in a car that cost far less than it could have, AND has it's own truly unique look!