Lay, laid, lain, or lie? A common meaning for "lay" is "to put" as in "lay brick." Past tense would be "laid brick." "Lie" is an intransitive verb (no object) as in "lie asleep." Most people miss the difference between "lay" and "lie" because "lay" can also be the past tense of "lie." So you can say "lay" asleep, if you are speaking past tense, but if you are speaking present tense you would say "lie asleep." You would be incorrect to use "lay asleep" in the present tense. "Lain" is the past participle of "lie", so you would use it in verb forms like "had lain." Still confused?
Affect or effect? "Affect" is rarely used as a noun. An example of "effect" used as a verb is "effect a settlement."
Dove or dived? Both are common past tense. A word related by spelling is "drove," however "drived" is not a word. Likewise, other pairs are, "hung" and "hanged;" "proven" or "proved;" "snuck" or sneaked."
Some will insist that "biannual" means twice a year and "biennial" means every other year. IMHO, "semiannual" means twice a year and "biannual" - "biennial" are synonyms. The same goes for "bimonthly" and "biweekly."
"Principle" or "principal?" When "principle" is used, it's only used as a noun and when in doubt, look it up.
"That," "which" or "who?" Usually, "who" refers to people and "which" refers to things. "That" can be used to refer to people. Both "that" and "which" can be used to introduce clauses.
"Fulsome" may mean generous or flattering, "fulsome praise; lest I be thought fulsome"
The context will leave no difference between "in" and "into" in phrases like "went in the house." Similar is "on" and "upon."
"Old timers like myself" is a phrase that may appear grammatically incorrect, but this idiom is considered to be standard usage.
"One" has a formal ring when used as a non-gender pronoun. Mark Twain left us with this example of pronoun shift: "When one is learning the river, he is not allowed to do or think about anything else."