A, an: Use a before words beginning with consonants or consonant sounds, as in a bicycle, a morning drink, a historical work, a unity of mind and soul--the long u creates a consonant sound. Use an before words beginning with vowels or vowel sounds, as in an elephant, an underdog, an honorable woman--the h is silent, so the o sound demands an.
Accept, except: Accept is the verb that means "to receive"; except is the preposition that means "other than." For example,
The winners will accept their trophy next week.
Everyone has completed the work except Hugo.
Affect, effect: Affect is the verb meaning "to influence" or "to have an effect on"; effect is the noun meaning "result" or "impact." Effect can also be a verb that means "to bring about." For example,
By increasing taxes, the government can affect the economy positively.
There will be a serious effect on your grades if you fail to turn in the assignment by tomorrow.
Nothing effects positive change in the economy like increased spending by the government.
A lot: A lot is always two words.
Amount, number: Amount is used to indicate quantities that are measured; number is used to indicate quantities that are counted. For example,
The amount of grain sold by farmers does not always mean an increase in their income.
The number of cows sold by farmers does not always mean an increase in their income.
Grain cannot be counted, but cows can.
Being as or being that: Both expressions are informal and wordy and should not be used to replace because or since in formal writing or speech.
Lead, led: Do not confuse lead the element with led. Use led as the past tense and the past participle forms of to lead. For example,
The team led the game throughout.
We were led into the problem when we followed the wrong car.
I used a lead pencil to write the paper.