To kick it off

I'm pretty tired of some spelling (and usage) mistakes people make, so I decided to start a blog about it. I'm talking about really basic mistakes that can be avoided pretty easily. To kick off, I'd like to share an Enid Blyton story.
(I read it a long time ago and I'm just writing it as I remember it)

One day an elf was walking in the woods when he suddenly heard a strange chanting. When he saw that it was a magician making a spell, he quickly hid behind a tree to watch.

"T-O-A-D-S-T-O-O-L!" chanted the magician, and dropped a toadstool into the pot in front of him. "B-L-U-E-B-E-L-L!" he chanted, and this time dropped a bluebell into the pot. He went on with several other items, and after dropping the last one in, there was a big bang and he fell back.

Then, to the elf's surprise, the magician scooped up a handful of gold from the bottom of the pot. He then proceeded to repeat the spell and make more gold.

The elf immediately decided to make his own gold. Who would have thought that spells were so easy?

Once he had found everything necessary for the spell, he began chanting. "T-O-D-S-T-O-O-L-E!" he chanted, dropping a toadstool into the pot. "B-L-U-B-E-L-L!"

When he had put in the last item, there was a big bang and he fell back. Filled with excitement, he crept up to the pot and peered inside. To his astonishment, he saw inside, not gold, but a large dictionary!

So what's the moral of this story? Spell it right!

I'd be happy if someone could let me know whether it was an elf (or a goblin, or a whatever) and his name! (or just suggest a name)

Let's spell it right

I'm trying to put this in alphabetical order as much as I can...when there are two different words (as in the case of borrow and lend) I shall take the word that comes first to determine its place.

I am trying to provide short and simple explanations, but I cannot guarantee that they work for you! So when in doubt, do consult a dictionary.

Feel free to suggest any common mistakes that I may not have added yet. ;)

*****

You advise someone, but you give people advice.

If something affects you, it means that it has an effect on you.

To afford something is to have enough money to buy it. Something that you can afford is affordable.
An effort in the energy spent to do something.

Anyways is not correct, though it has crept into common English :(
The correct word is anyway.

You bathe, but you take a bath.

The right expression is to bear with something. (not bare)

Something that is boring makes you feel bored.

You borrow something from someone. That thing is not yours.
You lend something to someone. That thing is yours.

You breathe, but you take a breath.

We speak of open tournaments (anyone can join) or closed tournaments (only members of a certain association/group can join). A close tournament is where the result was close (it wasn't won easily).

A cloth is the fabric used to make clothing.
What we wear are clothes or pieces of clothing.
To clothe is also a verb: A piece of clothing clothes someone.
You need cloth to make clothes/clothing.

A compliment is praise.
A complement is something that completes or makes whole.
These two words can also be used as verbs, i.e.:
We can compliment someone (praise someone).
A cup of coffee can complement some home-made biscuits, making the biscuits taste better than if they were eaten on their own.

A deadline is the date at which you have to complete something (usually an assignment).
A dateline is found at the beginning of an article, stating when it was written. It can also refer to the International Date Line, an imaginary line in the Pacific Ocean where the date changes as you cross it.
(Thanks to Chang Yang for making me think of this)

You extend something to a certain extent.

When we say that there are few things in a box, we are trying to say that there are not many things in the box (less than expected).
When we say that there are a few things in a box, we are trying to say that there is something in the box (as opposed to nothing).
(Both still mean that there is a small number of things in the box)

An incident is an event that happens.
An incidence is an occurrence of that incident, or the rate of that incident happening.
Perhaps it would be easier to remember this:
The incidence of an incident = the occurrence of an event
(Thanks to Jeffrey Matisa for this suggestion - see comments)

It's is a contraction of it is.
Its shows possession: The cat is waving its tail.

To lose is the opposite of to win.
Loose is the opposite of tight. (the verb is to loosen)

Lost is the past tense of lose.
We usually say "I lost something" because the thing is already lost. (in the past)
A loss refers to something which has been lost, or the event of losing something.

You pay a price, and you win a prize.

You prove something by showing proof.

You respond to a question by giving a response.

When you have a cold, you have a runny nose.
If you have a running nose, it should not be the one on your face, it should be a fake one with legs! :P

Stuff is like furniture, it never takes an 's' "in plural"!
We say: a lot of stuff
or: a lot of furniture
without an 's' at the end of the word!
Other words that follow the same rule: work/homework, money

Something is tiring when it makes you tired.