Dr. B-F's Grammar/Spelling/Usage Tips
 
First of all, take pride in and be careful about how you write, punctuate, and spell. Your writing is quite often the first means by which other people get to know you, so if they see something sloppy they may not get a very good first impression. How carefully proofread your resumé is, for example, could make the difference between whether you make the first cut in a job application process.

These aren't set down here in any particular order, for the most part. It might be a good idea to keep this, and add to it yourselves when you come upon any tricky usage questions. Let me know if you think this list needs to have other things on it, and I can update it for future generations of students!

 
1. Use phenomenon when speaking of a single thing - it is the singular form of phenomena. The same goes for criterion and criteria, medium and media. It is really incredible the number of people who don't seem to know the singular forms of these words, or, if they do, they don't use them when they should!

2. Data is plural (datum is the singular). So, we talk about 'these data', not 'this data'.

3. Only use 'it's' when you are contracting 'it is' (or 'it has'). For example, the second 'its' in 'It's lost its smell' is possessive and should not have an apostrophe between the 't' and the 's'. This may be the most common mistake I find in student writing. By the way, its with an apostrophe AFTER the s is never right!

4. Learn to spell (and say) the word 'asterisk' properly (this thing *). Many people spell and/or say 'asterix', but the only Astérix there is is a Gallic warrior in French children's books, as far as I know! There is a little rhyme that goes like this, which might help you to remember the correct pronunciation:

Little Mary donned her skates
Upon thin ice to frisk;
Wasn't she a silly girl
Her little * ! (ass to risk!) 5. Use a hyphen between two words used together that function as an adjective before (not after) a noun, but don't use one to connect adverbs ending in 'ly' to the words they modify (e.g., 'Results revealed a left-hemisphere advantage in the dichotic-listening task.' but 'His strongly held views were very odd.').

6. Words to tell the difference between:

adverse: an adjective - modifies a noun, means 'unfavourable'
averse: also an adjective - usually followed by 'to' and means having an active feeling of repugnance or distaste. She is averse to studying biology because it has an adverse effect on her mood.

affect: can be a verb, meaning 'to influence', and, less commonly, 'to feign' (to pretend) and can be a noun, meaning, in psychological jargon, outward emotional appearance.
effect: is usually a noun, meaning 'result', but can also be a verb meaning 'to bring about'.

all ready: means 'all set to go'
already: means 'previously'

a lot: is right
alot: is wrong

all right: is right
alright: is wrong

awhile: is an adverb, so can modify verbs. 'Let him sit awhile.'
a while: is a compound of an article and a noun, and can't modify a verb, but can be the object of a preposition. 'After a while, he began to snore.'

between: use when talking about two things
among: use when talking about three or more things

amount: use when talking about quantities that can't be counted
number: use when you talk about things that can be counted

cite: to reference an article or manuscript (to cite an author's work)
site: a location (a building site)

complement: to go with, or complete
compliment: to flatter or say nice things about.

less: use when talking about general amounts
fewer: use if you can count whatever it is

imply: means to suggest or state indirectly
infer: means to draw a conclusion

lie: is an intransitive verb (one that doesn't take an object) meaning to rest on a surface or recline. (I was tired, so I lay down for a rest. The lecture notes were lying on the floor. He had lain on the forest floor to rest.). The confusing thing here is that the form of 'lie' to use in the past tense is 'lay'!
lay: is a transitive verb meaning 'to put or place something'. (I'm sure I laid the papers here somewhere. He interrupted me while I was laying the baby down.

peruse: means 'to examine closely' but people seem to use it (wrongly) to mean 'to skim over' these days.

principle: is a noun meaning 'a basic truth or law'
principal: is a noun meaning 'head of a school' and also an adjective meaning 'most important'

regardless: is right
irregardless: is wrong, but 'irrespective' is fine

relation: describes a connection between things
relationship: describes a connection between people

that: use for restrictive clauses (ones that need to be there for the meaning of the sentence to be clear - they are not set off by commas, e.g. 'He needed the clothes that were washed.')
which: use for nonrestrictive clauses (ones that contain nonessential information, and are set off by commas, e.g. 'She needed the shoes, which were in the closet, to be taken to the shoemaker for repairs.')

there: most usually an adverb specifying place (I put it there.)
their: is a possessive pronoun (Jon and Neil washed their car.)
they're: a contraction of 'they are' (They're in the boat.)

your: is a possessive pronoun, e.g. 'Pick up your coat, please!'
you're: is a contraction of 'you are', e.g. 'You're in the top ten candidates for the award!'

Other Things:

due to: should not be used as a preposition meaning 'because of'. 'The seminar was cancelled because of (not 'due to') lack of response.' It is acceptable to use it as a subject complement after a form of the verb 'be'. 'Her failure was due to lack of work.'

comprise: to contain or embrace the parts of some whole. "The Psychology Department comprises faculty, staff, and students.' This word is often used instead of 'made up of' or 'contain' and is confused with 'compose'.

since: should be used for temporal (time) relations, not to mean 'because'.

while: avoid using this word when you mean 'although', or 'whereas'. It means 'at the same time that'.

where: avoid using this word when you really mean 'wherein' or 'in which'.  "Where" should be used only when you're referring to a location.