Many times, adding a suffix to a word means doubling the final consonant. When a word has one syllable, with one vowel followed by one consonant, like GRAB, double the final consonant before adding a suffix beginning with a vowel, like "-ING." The result is GRABBING. Another example is BIG. To add the suffix "-EST," double the final consonant to get BIGGEST. This rule doesn't apply, for example, to words with two vowels, like READ, which isn't spelled READDING or ending with two consonants, like SING, which isn't spelled SINGGING.
When the "CH" sound is at the start of a word, spell it "CH," such as the words CHASE and CHOICE. When the "CH" sound is at the end of the word, use "TCH," such as the words PITCH and FETCH. One odd example is the word TCHOTCHKE, but its use is not common.
In a two-syllable word with a short vowel, there is one group of letters that receives a special rule. When the letters "B, D, G, M, N, or P" follow a short vowel in a two-syllable word, like DRUMMER, double the consonant. Other examples include RABBIT, NUGGET, HAMMER and PEPPER. One way to remember these letters is the acronym "Big Dogs Give Me No Problems."
When a word ends in the hard "C" sound, it can be spelled with either a "CK," such as the word DUCK or just a "K" like in the word BARK. There is an easy rule to follow to know which one to use: if it is a short vowel, use "CK." Examples include DECK, MOCK, and HECK. If it is any other sound, such as a long vowel, "L", or "R", use "K." Examples include JERK, MILK, TANK and BIKE. One example to this is the odd word YAK. It does not follow the rules.