Learn to use the search feature on your word processor, which can save you several hours of drudgery, especially on a long paper. All modern word processing programs have this feature; look in the manual or the online help facility (under "search," "find," "look," etc.) for instructions. Then compile a list of your personal gremlins, and try to figure out how many of them are machine-searchable. You'll have to run a separate search for each type of error. As you make each search, you'll still have to remember or look up the rule, but you'll have to look it up only once for each error type, instead of several times as you would in human proofreading. And the machine will locate the errors far faster and less fallibly than you can. Furthermore, unlike a purchased grammar checker, your own customized search routines won't waste time looking for mistakes you don't usually make. Here are some possibilities:

• Proper names and scientific terms that aren't in the spell checker's dictionary. The computer can help you ensure that [Ben] Jonson isn't spelled like [Samuel] Johnson; that the composer's name gets transliterated from Russian consistently, and not several different ways (Tchaikovsky/Tschaikovsky/Tschaikovski/Tchaikowski/Tschaikowski, etc.); that other words are correctly spelled in their plural forms; or that foreign words are accented correctly and consistently.
• Words that are in the dictionary but that you know you tend to misuse, e.g., portray (for depict or represent) or valid (for correct or true). If you don't have a grammar checker, you can also use the search feature to check for commonly confused words like there/their/they're, its/it's, affect/effect.
• Apostrophes. You may have no problem with apostrophes, but some people consistently misuse them. Unfortunately, there's no way to check for missing apostrophes, but you can at least make sure that the ones you've used are correct--that singular possessives and plural possessives don't get confused, and that you haven't used 's to form ordinary (nonpossessive) noun plurals.
• Infrequently used punctuation marks (commas, alas, are too frequently used for a machine search to be worthwhile). If you're not quite certain about the rules for using the semicolon (or the colon, or the dash), you can have the machine locate all the instances in which you've used it.
• Combined punctuation. You can have the machine search for combinations that shouldn't occur in American English, like [",] or [".] or [,   (]. (The rules: commas and periods go inside quotation marks; commas, if needed, go after a closing parenthesis mark rather than before the opening parenthesis mark.) If you have trouble with the rules for punctuation leading into a quotation (a comma? a colon? no punctuation at all?), you can efficiently find and check each instance in your text by searching for [[space]"] (i.e., the beginning of a quotation).

True, most machine-searchable errors are small ones. But cumulatively, even small errors can irritate your reader. There's really no excuse for confusing it's and its, now that you can use a 90-second computer operation to correct the error. And the more you practice using the search function to build your own, customized grammar check routines, the more ways you will find to use it. For example, a grammar checker can't identify "comma splices," and using the search function to look at every comma is inefficient; but if you know you have a tendency to "splice" together two independent clauses with [,   however] you can certainly search for [ ,  however] and try to decide, in each instance, whether the combination is being used legitimately (as an interpolation within a clause) or improperly (to join separate clauses). Let the machine do the scutwork, while you, as the human being, interpret the rules, make the judgment calls, and invent creative revisions.

WARNING: Most word processors have not only a search feature but also a replace feature, which will automatically replace one string of characters with another string throughout the document (for example, changing it's to its). Don't use the automatic replace feature until you've had some practice with searching and manual replacement; and when you do use it, think very carefully about how you design your string. Maybe in some instances you really did mean it is.

Even though your computer is an efficient tool, be wary. Spell checkers and grammar checkers follow rigid checking procedures and don't allow for exceptions. Some kinds of grammatical errors, such as dangling modifiers, can't be machine-checked because they involve mismatched meanings--and the machine, of course, doesn't understand meanings. You can't count on even the latest grammar checker to catch even half of your errors. No grammar checker can yet account for the variances and exceptions in English grammar. In addition, some grammar checkers have been programmed to do specific things, such as flagging all passive voice verbs, that may make you think you have an error when you don't. If you do have an error, the grammar checker may not tell you how to fix it. And your spelling program won't catch a correctly spelled word misused for another, as when you type "the" for "then," nor will it see any difference between "it's" and "its," or even "pubic" and "public." If a word is spelled correctly according to the program's dictionary, then it's accepted. So use those aids, but be sure to double check your essay afterwards. See Proofreading.

Contributed and edited by Nancy Mann, of the University Writing Program. Many thanks for her contribution of this tip.