There are many considerations that need to be observed when deciding what kind of grass seed to buy. Some grass types require much more maintenance than others, and most grass requires a particular climate to thrive properly. You also have to think about the characteristics of your lawn, and make sure there are not any issues that might become hindrances.
Bunching or creeping?
One of the first things you need to decide is whether you want bunching grass, or creeping grass. Bunching grass spreads in an outward pattern using shoots that spring up near the spot where seeds were planted. Creeping grass creates stems that spread out under the ground, and sprout at periodic intervals. creeping grass is a bit tougher than bunching grass, and if your lawn is likely to get some heavy use, it might be the better choice. Bunching and creeping grass also look a little different on the ground, so you should look at examples of each type and decide which you like best.
Climate and soil concerns.
You need to make sure you buy a grass that thrives in your climate. This is one of the most important things to investigate before purchasing grass seed. Some grass is very intolerant of cold weather, and some grass doesn't respond well to dry climates. Unfortunately, if you live in an area with a relatively extreme climate pattern, this can greatly narrow down your choices.
Poor soil can also be a very debilitating problem. Some grasses are hardy and can tolerate it very well, but you may not realize you have poor soil until your grass fails to grow, or grows in and looks unhealthy. Having your soil tested, and then adding the right kinds of nutrients when you're fertilizing can be helpful in avoiding this issue.
The texture of your grass can be an important concern for some people. Wide bladed grasses are thought of as coarse grasses, while narrow bladed grasses are considered fine. This is mainly just a question of personal preference, and one is not necessarily better than the other. One of the few situations where this really matters is in the planting of golf courses. In that sport, the texture of the grass plays a pivotal role in determining the speed of putting greens.
There are pretty big differences in the color between different grass types. If you want a vibrantly green lawn, you have to select a grass that can produce that kind of color, but this issue is also a question of proper maintenance, and choosing a good grass for your situation. Some grasses are very intolerant of shady areas for example, and that can cause an unhealthy color.