Brightness in moderation...

I am a big "bright color" person..have to have an element of bling in my design and I think it definitely leads to the 'wow' factor in a space. Keeping it bold and bright doesn't mean everything has to be the same tone, brightness always goes well with neutrals. Either have all the walls neutral with a blob of a big colorful couch or have a big focal wall bright keeping the rest neutral. Its always preffered to go the 'big buck' route...everything expensive or fixed should be neutral whereas the rest should have accents of color and brightness. In a larger space, walls & bulky furniture pieces are the big buck items and throw pillows, end tables/ottoman and rugs are accents.

Never paint all the walls in a bold color, this might make the room look smaller. If you really have to do it, go this route... create a pattern on the walls (as below) that matches the floo, making it look interesting and yet colorful.
If you are a painting expert try merging a darker and lighter tone together as below.

Paint the niches or depressions in a room to create frames.

Don't restrict yourself to walls only, you can also go up on the ceiling or down on the floor with the same accent color.

Try and experiment with tints and tones...Add a bit of neutral or contrasting color you are using into the brighter color and see the difference. Below is a perfect example of how when pink was mixed with a bit of grey(contrasting color) gave a perfect, more cozy pink.

Sliders can be accents too. The red partition is actually a mobile accent in the picture below.

Yellow paired with brown makes a rustic accent...

Yellow contrasted with white can be very modern...

Black and white goes with every color...

Red is never enough....

Bright accent wallpapers make it more chic!!!