I really enjoy learning more about language and grammar. I am not, by any stretch of the imagination, a grammar nerd. I do, occasionally, joke with friends about grammar mistakes, but mostly when I spot them in mass market advertising. So, having said that I am not an expert, here are my favorite grammar rules and how they apply to your resume and cover letter.
- The semi-colon is used to join two complete sentences; it is often misused. My advice is to just ditch it altogether. Replace it with a period and make it two different sentences. If it doesn't read well, just re-write it until it does.
- The colon has some limited uses: preceding a list, joining two complete sentences with a related first point, adding emphasis at the end of a complete sentence, or before a long quote after a complete sentence. As with the semi-colon. Don't use it! Just re-write it.
- Using a preposition to end a sentence with. Of, in, at, before, for, and on are all prepositions. When I was growing up I was always told to never end a sentence in a preposition. Well, if I had Google back then I would surely told my mother, "That is the sort of pedantry up with which I will not put!". It is not necessarily wrong to end your sentence in a preposition. Guess what my advice is? Re-write your sentence so you don't need to end the sentence in the preposition, and you don't have to have it sound "with which-ey".
- Apostrophes can be your friends, if you use them correctly. Believe it or not, the apostrophe is the culprit behind most (likely accidental) grammatical or spelling errors I read in cover letters and resumes. Print your resume, highlight every word that has an apostrophe and make sure you are using it correctly - as in a contraction (can't, shouldn't) or to show possession.
You may want to go against my advice and use a semi-colon or colon, as an example, because you are sure you are correct. Just remember, the person reading it may think you're wrong. Keep your writing simple and avoid anything fancy.