Experience has taught me that learning rules for spelling--especially spelling words in English--is little other than a waste of time. I remember memorizing the "'I' Before 'E'" rule in grade 3. Then I learned the first groups of "exceptions" in grade 4. In grade 5 they added more exceptions to the rhyme, and then, in grade 6, I learned a 22-word sentence that included exceptions the all the other exceptions already present in the quaint little rhyme. So, the first rule of spelling in English is this: Don't use rules for spelling in English. Let me elaborate: Here is the rule: "'I' before 'E'" First exceptions: "except after 'C'" Second exceptions: "unless ('unless' and 'except' mean the same thing) it sounds 'A' as in 'Neighbour' and 'Weigh'" Now, here is a sentence in which every word with a paired 'I' and 'E' is an exception to all three parts of the rhyme above: "Neither the weirdsheik, nor the feistyforeignfinancierseized the scientific opportunity to observe the ancientspecies in theirleisureheight." What's worse is that this list of exceptions is not even close to being exhaustive. There are still dozens (if not hundreds) of exceptions out there. Wikipedia has a pretty good list if you're interested in finding more.
Conclusion: there is no "'I' before 'E'" rule; you have been "myth-informed."
So, since you really can't memorize rules to teach you how to improve your spelling, what it comes down to is that you need to memorize the spelling of the words. Below are 7+ helpful hints that will make the memorization of the spelling of words a little bit easier.
Hint #1 A: Break the word or words into smaller portions to find out what other words are included in the spelling. Sometimes the inner word will give a hint as to the meaning of the whole word. For example, if you are confused by "Their," "There" and "They're," you can drop the "T" from the first two. "Their" becomes "Heir" as in "Heir to the throne." Both "their" and "heir" indicate possession. Without the "T," "There" becomes "Here." Not THERE, over Here. Then, if you can remember that "They're" is a contraction for "They are," everything should fall into place for you.
Hint #1 B: Look for meaning in the smallest part of the words that confuse you and spell each according to its meaning. If you get confused with "Which" and "Witch," or "Whether" and "Weather," keep in mind that "Wh" often indicates question words: "What," "When," "Whence," "Where," "Wherefore," "Whither," "Who," "Whom," "Whose," "Why," and their variations and whatnot, (the exception, of course, is "How") then you can see that "Which" and "Whether" are also question words, and that idea will help you remember the other two words.
Hint #2: Look into the history of the word in question. You may find that its pronounciation or its history gives hints about its spelling. "Chihuahua," for example, we pronounce as "chi-WOW-wha." Originally, however, it was pronounced more like the way it is spelled: "chi-HOO-ah-hoo-ah." When you see that the pronounciation resembles its spelling, the spelling will be easier to remember.
Hint #3: I know. I've also puzzled over the question, "How can I look up a word that I can't spell?" It's true, though. Mom was right when she used to say, "Go look it up." I keep a dictionary right at hand for just such occasions. I even had to look up the word "occasions" just now.
Hint #4: Start to learn how words are spelled. With practice, you'll memorize the spellings without having to learn any rules. (Ah! "occasions" has two "c's" and only one "s.")
Hint #5: Don't be afraid to ask a friend. I've been teaching English for 25 years or more, and I still, every once in a while, am left with the option of asking a colleague how to spell a word that I can't find in the dictionary. Have you ever tried to look up the word "mnemonic"? If you don't know that it begins with a silent "m," you're in for quite a challenge. More importantly, I can't count the number of times someone has asked me how such-and-such a word is spelled. It's is no crime to seek help.
Hint #6: USE THE SPELL CHECK! It's there for a reason. And, while it may be a detriment to people actually learning how to spell words, its use can still he a great help in making all of us look more professional by simply catching typing errors, if not all-out errors.
Hint #7: Stop using texting lingo. Spell the words completely. It may take two or three seconds longer to say what you want, but you'll be exercising your brain. Is there a problem with that?