If you do your informational shopping on the internet, narrowing down your search, note that you must actually test the machine before you buy. Bring your own knits and heavy and lightweight fabric samples and even your quilting for a real life test. Have kids? Bring along some jeans for an idea how the machine will handle thick, dense fabrics. Use different colored threads on top and bottom so you can see how the tension is working. Ask questions and take notes if you need to. Don't be pressured into an on the spot purchase.
After you have determined your budget, a number of machines will fall within your range. Don't just go with the name brand's reputation as companies have been bought out or taken over. Some companies have a great reputation built upon their high end machines manufactured in Germany or Switzerland, with mid and low priced machines made in China. You can find a solid mechanical sewing machine for $180 and up. Moving to the computerized or electronic machines, look to pay $500 and up. Top of the line Husqvarna or Bernina machines can sell for up to $3,000.
It is important to know how you will be using the machine currently and in the future. Make a list of what you then will need, what you will want, and the extras that would be lovely to play with. Try out the machine. For basic sewing, a mechanical machine will do just fine. For decorative or tailoring sewing consider stepping up to a computerized or electronic machine.