The way you write a word in English is - more or less - the way you spell it. The letters we write on the page or screen represent sounds, not meanings. So, however difficult a word is, we always have some idea of how it's written. We are never in a situation where we have completely no idea how to spell a word. If we know how a word sounds, we always know approximately how it's spelt. Here are some examples: Sometimes it's a question of getting the vowels right. For example, is it 'permanent' or 'permenant'? Is it 'separate' or 'seperate'? Or it's the order of the letters. Weird or wierd? Psychology or phsycology? Or other times it's whether or not to double a letter: necessary or neccesary? Or occasionally, it's a case of which letter to use in situations where two letters can make the same sound, for example, intense or intence? If we're not sure of a spelling we just have a go at writing it, and see how it looks. If we're writing in a digital format, the spell check will correct it. If we're not, we have a look at what we've written, and if it looks wrong we have another go or check in a dictionary. And if we do get the spelling slightly wrong, people will probably still understand what we mean. By the way, if anyone's wondering : the first spelling in each of those pairs of words above is the correct one.

English is a bit different to Chinese because we use an alphabet and it is not a character based language. If you can't remember how to spell a word you should look it up in a dictionary based on how you think it is spelt from the pronunciation. But this is a problematic issue for learners (and native speakers when we are growing up and learning how to read and write) because in English the spelling often does not match the pronunciation. A lot of people (including native speakers) would probably just attempt to spell it without looking it up. It will likely be understood, but obviously this is a very unsatisfactory solution because good spelling is important if you want to have a high level of written English. If you really have no idea how a word should be spelt from its pronunciation, well then you can always think of a synonym or similar word that you do know how to spell. Or if you have an advanced level, restructure the sentence to convey your point in such a way that it makes the word you don't know how to spell unnecessary.

The only way to do it is to sound the word out and guess based on words you already know. Most words are spelt fairly close to the way they sound. If you type a rough guess into a search engine or spell checker it should be able to figure out what you mean. If your first attempt doesn't work then you should try a couple of spelling variations. If you still cannot find the correct spelling of the word then you can try and find the word using its meaning.

I cheat! I simply open a program that has a spelling check feature and write it there. But when I was a child, I had to use the dictionary.

I look up the word in a dictionary.