Once you've narrowed down which type of chair would fit your home in terms of type, material and style, you should also think carefully about how many you'll need. This depends most directly on the size of the table you're looking to place the chairs around.
The smallest tables in the kitchen will often need one or two chairs.
Larger round or square tables do well with four chairs.
Dining tables get a little more complicated, as they usually have the two chairs on each end, but how many chairs you can fit around the table depends on the length of the table. Measure how long the table is, and make sure you know how wide the style of chair you intend to buy is as well. A general rule is to give about 6 inches or more on each side of the chair to give room for elbow space.