Probably the most important decision you have to make when buying carpet is what style you want. Or put another way, what you want your home to look like when it’s done. Are you interested in something casual or formal? Do you want a carpet with many colors in it or do you want it solid? Do you like a long shaggy pile or do want the shorter, lower profile type? Before you even head to your local store, these are things you should give some thought to.
All the other variables (like the density, color or stain resistance) are secondary until you figure this out first.
The way I would start my shopping experience is to visit some local carpet stores. If there are any in your area that has large warehouses, that is your best, first stop. After all, it is too hard to visualize what a house full of carpet will look like off tiny samples. Big warehouses have rolls of carpet and tons of remnants in big chunks so you can see what a big piece looks like.
If you are able to take some rough measurements, do so and bring them with you. If you have a set budget (and most people do), this will help keep you looking at products you can afford. There’s nothing worse than falling in love with a high end carpet that you find out later is twice your budget!