Listen, spellcheck is great. It saves us time and catches most of our major errors and oversights. But you cannot reply on spellcheck alone. You have to proofread, too. There are dozens (if not hundreds) of errors that your spellcheck won't catch. Here are three sets of tricky words to look out for:
"Its" (no apostrophe) indicates possession. As in: "The guacamole you made was okay, but its consistency was really weird."
"It's" (with apostrophe) is a contraction for "it is" or "it has." As in: "It's extremely rude to remark on the consistency of my guacamole." or "It's been seventeen years since I last made guacamole."
"Their" is possessive. As in: "The chefs at that new restaurant are great. The consistency of their guacamole isn't unusual at all."
"There" refers to a location or an abstract idea. As in: "Look at that bowl of guacamole over there." or "There are three components to exceptional guacamole, the most important of which is consistency."
"They're" is a contraction for "they are." As in: "Our new neighbors seem nice. I'm glad they're enjoying the guacamole."
"Farther" refers to physical distance. As in: "I'll bet I can throw this bowl of guacamole farther than you can."
"Further" refers to metaphorical distance. As in: "This guacamole seems unusually smooth. I'll need to investigate further."
More tips to come...