Spelling words correctly is very important if you want to communicate without any misunderstandings - or if you want to appear clear, professional, intelligent and well-educated.
Spelling mistakes can cost you dearly!
For example, if you were to apply for a job but make careless spelling mistakes, this would reflect poorly on you, and could mean you'd miss out on the job all-together.
Why spelling is important
Correct spelling is important as it allows you to express yourself clearly to others so they understand the meaning of what you are attempting to convey. If there were no spelling rules in writing, and people spelled words as to how they sounded, or how they felt certain words should be spelled, there would soon be misunderstandings and frustration as people failed to effectively express themselves and understand each other's needs and ideas.There Are Many Rules Which Help Towards Correct Spelling
Rules such as "I before E, except after C, unless it says A as in neighbor and weigh," can be of great use in learning how to spell difficult words. For more such rules, click here. Some words, due to tricks of history or obscure origins, will always be difficult to spell as they are unique in some way and rules do not apply to them, such as 'necessary,' 'dispatches' or 'restaurant.' I always break down the latter to 'rest-au-rant,' as in arRESTing an AUstralian RANTing in a restaurant, like this guy: