& for "and."

And etcetera [also, and etc.].  Try to avoid overuse of "etc." 

Awesome .

Bad [if used to mean "good" or "powerful"].

Bunch of [except when referring to flowers or root vegetables]  [also, buncha, whole bunch of, whole buncha].

All contractions, such as don't, won't, isn't, can't, it’s, couldn't, etc.  The exception is in common titles, such as "Dr. Garcés," "Sgt. Smith," "Ms. Eaglefeather," "Rev. Trung" or "Mrs. Ayoub" when the name is mentioned.  

Cool [except when the word refers to temperature].

Cuz or ‘cuz for either "because" or "cousin."

Damn or damned [except when the word is used in a strict religious context].  

Going to, gonna--[use "will" instead].

I think .

In my opinion, or In my humble opinion.

Kill [except when writing about someone actually taking a life. Obviously, making idle written death-threats, even in jest, could violate Texas law and University regulations and is strictly prohibited in academic writing]. 

Lots of [also, lotsa, a lot of, alot], except when writing about auctioneering or the wholesale business. 

Man, or Mankind, when referring to all humanity [except if you are referring to males only].

Nice.

Nowadays [also, now a days, now days, these days].   

All online or text message abbreviations (e.g., @ for "at," "BTW" for "by the way," "b/c" for "because," "LOL" for "laugh out loud,". "W/" for "with."

All racist, sexist, homophobic or discriminatory language [For most undergraduate work please consider "bleeping" out this type of language with the ellipsis (three dots) even when it appears in direct quotes, The only exception might be when your writing directly addresses the problem of this kind of language itself].

All slang, including slang uses of ordinary words (e.g., "That's totally weird").

Smileys :)  ,  :(

Stuff [except as a verb: to "stuff" a couch cushion, a plush animal, a chile pepper, etc.]

Stupid [also, dumb, crazy, idiotic, cracked, nuts, or similar put-downs].

Try and  [use "try to" or "attempt to" instead].

Tuff [the correct spelling is "tough"], except in the context of geology. 

All vulgarities, obscenities and profanities [except in direct quotes].  Normally, do not use any word that you would not say in front of your parents or in front of a religious congregation]. 

Was like, when used in writing dialogue  [e.g. "So he was like, 'Don't bother me'"].

Wicked [except in a religious context, to refer to a person who is morally evil]; wicked curves; wicked cool.

You or your  [except when used to directly address a specific audience of readers].