Grammar
Style guide 
Comparative adjectives
One-syllable words take -er and -est to make them comparative.
hot, hotter, hottest
Three or more syllables are preceded by more/less and most/least.
beneficial, more beneficial, most beneficial
The rules are not as clear-cut with two-syllable words. Those ending in -y tend to take -er and -est, and the rest take more/less and most/least.
lazy, lazier, laziest; grateful, more grateful, most grateful
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Other grammar tips include:
dangling modifiers
me, myself, I am
prepositions - in and at
who and that