Where to start? How to avoid a decorating mistake. Timing is everything!

I've been helping out a friend with her condo decor. SO far we have painted her living room, kitchen, dining area.
This weekend we are going to choose new carpeting for her bedrooms, hallway, and staircase. We are also going to choose a color for her bedroom.

It's important, when working with a budget to use your head.
There are only so many decent inexpensive carpets out there...
There are thousands of paint colors to choose from.

Therefore it is easier to find a paint to compliment your carpet choice than it is to find a carpet (with in your budget) that compliments your paint color choice. One should choose the carpet first, then choose the paint color NOT the other way around!