Let's talk about words to avoid in your game writing (and, as a bonus near the end, what not to kill). These words and phrases generally produce weaker writing, so doing a find-and-replace for them prior to turning in a project makes the whole thing stronger. It also cuts a surprising number of words, if you find yourself over wordcount.

Will. This is the big one! RPGs should be written in the present tense, not the future tense. You don't say "The ogre will smash the first PC to walk into her cave," you say "The ogre smashes the first PC to walk into her cave." Before turning in anything, I do a word search for "will" and cut them (unless referring to a Will save, a person named Will, or in a useful word like willingly). If you take only one point away from me today, make it this one: kill will!

Redundant Words. There are several words and phrases that are redundant, and can be cut or simplified. Search for these phrases, and replace them with the shorter version. Personally, my biggest offender from this list below is "in order to," which I have to find and delete a lot.)

* Replace "in order to" with "to". 
* Replace "is/are willing to VERB" with the appropriate version of VERB. 
* Omit "tend to," "try to," and similar. If you mean the PCs can attempt some sort of check, state what happens for PCs who succeed or fail at such a check.
* Replace "by means of" with "by" or some other construction.
* Look carefully at "able to" or "can"; there's probably a better construction. This is often used to describe how PCs can make a decision or a check something. Of course they can; that's what being a PC is all about. Instead reword to talk about what check is needed, and its results for failure or success.

May. I have a fellow developer who absolutely hates the word "may." He calls it weak and inappropriately permissive. He kills it whenever possible, replacing it with either "might" or "can". (and, if it really ought be replaced with "can," look at the advice above).

But Leave Room! Many sites about good writing say to avoid "weasel words" like saying something is "one of the world's biggest cities" or "one of the oldest books on undead." Instead, these sites say, be forceful and decisive! State clearly that you have the biggest city in the world or the oldest book on undead! For RPG writing and world-building, however, this is often poor advice. It puts you into a box it's hard to escape. Once you've flagged something as the biggest city in your world, you've just made it impossible to invent a bigger city elsewhere--and you might really want to sometime down the line. Worse, you've made it harder for your readers--the GMs and ultimate users of the game--to adapt your world to their visions and additions. Overly decisive world-building language sets boundaries, and you should be very intentional whenever you do that. Often, hedging with phrases like "one of the largest," "one of the most significant," or "among the oldest" works best, and is appropriate for RPG writing. Or, even better, consider alternates that are more descriptive (like "Trade Hub of the North") or sound a bit like in-world marketing (like "Beacon of Religious Liberty").