The kids finally laid down in the adjoining hotel room, leaving the weary parents to their complementary bottle of wine.
2 errors: Laid should be lay, which is the past tense of the verb lie, meaning to recline (Webster's New World College Dictionary elaborates with nine additional, nuanced definitions). The confusion kicks in, of course, because lay is also the present tense of the verb that means to put down, as in The chicken lay an egg. Complementary should be complimentary, meaning free or on the house. Mistakes involving lay and lie and complementary and complimentary are among the most common.

The principle themes of For Whom the Bells Toll was lost on the students.
3 errors: Principle should be principal, meaning the main themes. A handy memory device is to remember the a in main and in principal. (Principle and principal are homonyms, or words that are pronounced the same but have different meanings and spellings. There are more to come in the answers!) The correct title of the novel is For Whom the Bell Tolls. Was should be were because the subject is plural themes.

Foregoing pleasantries as he headed toward the door, Uncle Jerry parted with an abrupt, “I said my peace. See ya.”
2 errors: Foregoing should be forgoing, meaning to go without. Foregoing means to precede or go before. Peace should be piece.

Through shear determination, she studied to become an advance practice nurse while working full-time.
3 errors: Shear should be sheer. Advance should be advanced because the training is beyond what other nurses have. Advance refers to something at an earlier time. You have an advance directive that details your end-of-life wishes. Full-time shouldn’t have a hyphen (full time) because it’s an adverb. If full time is modifying a noun — She was a full-time student — then it’s hyphenated.

Its common knowledge aneurysms most often form in the abdomen, however, they can occur anywhere in the body.
2 errors: Its should be It’s. If you aren’t sure which you need, test whether the context makes sense with it is. After all, that’s what it’s means. However is incorrectly connecting two independent clauses, creating a run-on sentence. One solution is to change the comma after abdomen to a semicolon. Another would be to change the comma to a period and start a new sentence with However.

The homebuyers signed a waver against there agent’s advice and later paid a price.
2 errors: Waver should be waiver. There should their.

Tim’s forklift lessons immediately led to a part time job moving palettes in the beer warehouse.
2 errors: Part time should have a hyphen. Palettes should be pallets. Confusion over palette, pallet and palate is, understandably, common. Triple homonym action!

Known as a lose cannon, she also had skills in truly affecting change.
2 errors: Lose should be loose. That mistake, most likely one of haste, comes up more than you would think. Affecting, meaning to influence, should be effecting, which means to bring about actual change. You will frequently, and correctly, see effect as a noun. Side effects, effects of the recession, the law’s effects. But, as the quiz sentence demonstrates, it also can serve a verb.

If you do get a sunburn, put a cold compress on it, even a bag of frozen vegetables will work.
1 error: Another run-on sentence. A comma on its own is not sufficient to connect two independent clauses. Change the comma after it to a period and capitalize even.

After final exams we were at O’Rourkes where the editor of the college paper was drunk and playing Jimmy Buffet’s “Margaritaville” over and over on the jukebox.
2 errors: A comma is needed after O’Rourkes because the clause that follows isn’t essential in identifying O’Rourkes. Buffett is misspelled. Poor Jimmy and Warren. Their last name is often mistaken for a restaurant buffet.

His principal goal was to become a diplomat of the American College of Cardiology.
1 error: Diplomat should be diplomate, which has a meaning particular to medicine.

The realization they no longer would have access to his wise council effected them deeply.
2 errors: Council should be counsel. Effected should be affected.

He was a Navel man through and through and could never reign in his tendency to respond “aye, aye” to his wife.
2 errors: Navel should be naval. Your navel is otherwise known as your belly button. Reign in should be rein in, another classic pair that has earned legendary status for being confused.

The Joneses’ have been assisting neighbor Bob with planning his deck and construction is going at top speed.
2 errors: The apostrophe after Joneses is incorrect. Joneses, in this case, is a plural, not a plural possessive. A comma is needed after deck to clearly separate the independent clauses.

The restaurateur had a flare for German and Asian cuisines, but combining the two specialties did not draw the sophisticated palates she had envisioned.
1 error: Flare should be flair, another top 10, or at least top 15, confused pair. 

Bill was struck by lightening in 1999, peaking his interest in meteorological phenomenas.
3 errors: Lightening should be lightning. Peaking should be piquing. Phenomenas should be phenomena, which is the plural form. Phenomenon is singular. (Who can say phenomena and not think of the Muppets, even though they were singing Mahna Mahna?)

After earning his MBA, Roger pedaled time-shares for a living, getting farther and farther from his dream of an empire of fireworks stands.
2 errors: Pedaled should be peddled. Farther and farther should be further and further. The Associated Press Stylebook reserves farther for actual physical distances and further for when the sense is figurative — to a greater degree or extent.
Her testimony went further than expected.

It started out as a speakeasy, founded in 1926 in the throes of the Great Depression, than later became a cabaret lounge.
2 errors: The Great Depression started in 1929. Than should be then, meaning next in time.