Notice anything wrong with this picture? This is one of the small storage tubs we are using to house miscellaneous stuff. I have four of them and had great fun labeling them with my labeler. Yeah. I noticed this morning that I misspelled "extension." Happens to the best of spellers. *sigh* I need to go find my labeler...
I usually see spelling and grammar errors immediately. I can't help it. I can't NOT see them. I'm an excellent speller and I have an excellent understanding of grammar rules and usage. Also, because of my high school background in journalism and being on the school newspaper staff, I'm a very good proofreader. I've been proofreading for people half my life and I've also done some copy-editing for folks.
I also know it's best to proofread your own work first and then have someone else proofread it. Your own eye can fool you; it's better to have a second unbiased proofreader. This is why writers have editors.
Spelling and grammar checker computer programs are great, but they are not perfect. This is why you should proofread again yourself after you run these programs.
A good example of this is my "crotch" story. When I was an Instructor at UTHSC for the Prosthetics and Orthotics Program, one of my favorite students was a terrible speller. He knew this and used his Spell-Check program all the time, but he didn't always proofread after he ran it.
The class was assigned to write up a summary report or "SOAP" note after they observed patients in a local clinic. I was grading the reports and the students knew I was a stickler for spelling and grammar. They were training to be medical professionals and often what they wrote would go in a patient's permanent medical record, and would be seen by other medical professionals. If you are a professional, then EVERYTHING you do should reflect that, especially your writing in whatever form it takes (letters, e-mails, etc.).
Anyway, I called the student to my office and asked him to demonstrate for me a "crotch" gait. He looked at me with complete bafflement on his face. There's no such thing as a crotch gait. Now there is such thing as a crouch gait, usually seen in patients with spastic cerebral palsy; they walk in a crouched position, often on their toes.
After letting him stutter and exclaim for a bit, I smiled evilly and said, "You didn't proofread your report, did you?" He admitted that he hadn't, but wailed, "But I Spell-Checked it!" He had misspelled "crouch" as "crotch" but he had spelled "crotch" correctly, so Spell-Check didn't flag it. And crouch was a word that he could spell correctly. (No, I didn't let him off the hook.)
So, what makes a good speller? I think some people just have more of a knack for it than others. My dad is a highly educated man, but a bad speller. I've been proofreading for him since my junior high school days. He spells phonetically. He's often lamented that a dictionary can't help you spell a word right if you don't spell it right well enough to look it up. ☺
There are some words that even I still have trouble with. I can never remember if "recommend" has one "c" or two until I write or type it out and look at it. I can tell by looking that one "c" is correct. Of course, if I remind myself that "re" is a prefix, then I can spell it correctly, too.
And grammar? Well, I think you have to study up on this a bit and make it a priority to learn and use it well.
All that being said, I never correct someone's grammar or spelling unless they specifically ask me to proofread a document for them. But I do lament and get my knickers in a knot over common and repeated mistakes I come across on message boards, blogs, and the media in general.
I find this website very helpful for word usage mistakes: Common Errors in English. This website is run by Dr. Paul Brians, a retired former Professor of English. There is also a book by the same name, but the website is updated frequently.
Another fun site, but not really helpful at all with learning how to handle grammar mistakes is this one: Self-Appointed Grammar Police. This is a UK website that pokes fun at media grammar errors.
So what do you do? How do you improve? Well, I currently have eight different books on my desk that cover grammar and/or punctuation, and writing style. I also have a dictionary and thesaurus handy. When in doubt or if you have a question have something handy so you can look it up. To me, learning spelling and grammar is an ongoing process; hopefully, I'll continue to always improve in both.
And then there are errors due to bad typing, but that's a whole 'nuther story (and I plead the fifth)!