The key to survival and scoring well is to type quickly and accurately. If you're not a touch typer yet, consider completing the tutorial first, which will teach you the basics. In drill mode, you also have the opportunity to practice the keys you did the worst on after each drill.
Some things to remember while playing are word canceling, where you hitto stop typing an enemy's word, and that enemies don't attack right away, so you have time to read over a target phrase and prepare yourself before you start typing when you're going for accuracy and high word scores. Word canceling is mainly useful for enemies that throw projectiles at you, but can also be used when you've started typing a slower enemy's target phrase while being rushed by a quicker one. You should also keep in mind that not all bonuses are good for you, particularly the Alien and Genre Dictionaries. The former causes weird spellings or spelling errors in target phrases and the latter can lock you into a barrage of very hard words. These don't award any extra points, so they're better left alone unless you want to gamble on getting an easy genre.
The game is played on rails, meaning you are moved by the computer according to a script. Although the tracks are set, you can influence which track you take when they branch by performing (or not performing) certain actions, usually saving a person from zombies. When the track splits, you'll go down one fork and miss anything on the other fork until the end of the chapter or if the tracks converge later. Some chapters will have multiple splits along the way, allowing you to choose an easier path or a more point-heavy path.
The guide pages are not meant to be read from top to bottom, as navigation is based on the choices you make in the game. Each guide page will list the routes at the top, if there are more than one.