Then and than
More commonly used as:
The most common misuse for these words is simply using the wrong one, or using only one without a thought about another word being more fitting.

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The definitions:

Then
-At that time: I was still in school then. Come at noon; I'll be ready then.
-Next in time, space, or order; immediately afterward: watched the late movie and then went to bed.
-In addition; moreover; besides: It costs $20, and then there's the sales tax to pay.
-Used after but to qualify or balance a preceding statement: The star was nervous, but then who isn't on the first night of a new play.
-In that case; accordingly: If traffic is heavy, then allow extra time.
-As a consequence; therefore: The case, then, is closed.


Than
-Used after a comparative adjective or adverb to introduce the second element or clause of an unequal comparison: She is a better athlete than I.
-Used to introduce the second element after certain words indicating difference: He draws quite differently than she does.
-When. Used especially after hardly and scarcely: I had scarcely walked in the door than the commotion started.

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Now that you've got the tools you need to start spelling correctly, let's work on the lesson portion.
Sadly, many of you find upstanding citizens seem to have trouble with deciding when to use which then/an. Either that or (I think this is the case) you do not find it necessary to use even the slightest bit of your brains to type and spell correctly. We live in a sad sad world, when children find it too time consuming to type two extra letters (you), when children find it pointless to learn English properly. *wipes a tear away*
Anyway, back to the lesson; sorry I got a little sidetracked ranting about your pathetic existances.

Now, if you read the definitions it should be very clear when you should which. In case you didn't read them, I'll give you examples of each used in a sentence.

Then - [I'll be ready then]  [She set her alarm clock, and then she went to bed]  [It cost $12, and then you have to add sales tax] 
Okay, I'm done giving the examples that were WRITTEN IN THE DEFINITIONS.

Than - [I like chocolate more than vanillia]  [He likes pickles more than she does] 
Okay, I'm too lazy to put anymore, because they'll just be pretty much the same as the examples in the definitions. Basically, with than, it's used as a comparison.

And so ends another episode of "Spelling with Miss Susie"


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