This text below is actually prepared for a friend whom i'll start to teach Turkish [and get Russian lessons in exchange=)]
But i thought : while i am at it , why shouldn't i post this on forum and help others too?

Here you are...

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General rules about affixes:

In Turkish the vowels are separated into two categories,
1.a,ı,o,u (low toned- i saw in TLC site they are called as "hard vowels" which is wrong to me)

2.e,i,ö,ü (high toned-and they call these as "soft vowels" and i think this also is wrong, you see these are not soft ; but in contrary sharper)

*if a word ends with a,ı,o,u ; the affix comes after would suit this and the same for e,i,ö,ü...

Forexample: Ayşe'ye , Arabaya , Göle , Okuldan , Şehirde

*if a word ends up with a vowel ; a combining consonant would come in-between any single vowel affixes come after.

Forexample : Araba(y)-a here "y" is used to combine the affix with the root.

Now , let's start with states of a noun ;

İsmin Halleri(cases of a noun)

single case(nominative) : no affix is added to the noun.
ex: Bir gemi gördüm.->I saw a ship.

-e /-a case(dative) : this indicates the indirect object
and gives the meaning of "to" in English , and tells direction.
ex: Okula git->Go to school.
Ev'e gel ->Come (to) home.
Buraya gel->Come here.
(literally:come to here)

okul-a
Bura(y)-a here "y"is used to combine the affix with the root because the root is ended with a vowel.

*In Turkish as a general rule two vowels don't come together as they do in English like : "School ,Goal ,etc."

You may come across with words like "Aile ,Aidat , Saadet etc." but keep this in mind that these words are originally Arabic.You may also come across with some combined words which are exceptions.

-i/-ı/u/ü case(accusative): this indicates the noun as the particular subject of an action.Therefore makes the noun direct object of the sentence.Most times there is no affix used for this in English as you know.Sometimes it also does the job of "the"in a sentence. Other times it makes such a difference on a given noun : "He" before affix "-i" ; "Him" after affix "-i"
ex: Ayşe evi beğendi.-> Ayşe liked the house.
Ali onu sevmiyor.-> Ali doesn't like it.
Ali okulu seviyor->Ali likes the school.
Ayşe O'nu(Ali'yi) gördü.-> Ayşe saw him.(here its obvious that "-i" is equal to the change made on the word "he". We don't say "Ayşe saw he" but we say "Ayşe saw him"
(!) Him is also used as O'na(ona) ; but in Turkish there are different affixes for these jobs as you see.
example for (!) : Tell him that i miss him.
->O'na , O'nu özlediğimi söyle.(i supposed we know who we are talking about , say Ali..so the letter "o" should be capitalized.)

o(n)-u (here "n" is used for combining)

In Turkish it's essential to use "-i/-ı/-u/-ü" if you want to mark a noun as the direct object in a given sentence.

-de/-da case(locative): This indicates our noun is present at a particular place.It gives the meaning of "at/on/in" in a sentence.
ex: Ali stayed at home .->Ali evde kaldı.
Ben Türkiye'de yaşıyorum->I live in Türkiye
Dairem Atatürk Caddesi'de.-> My flat is on Atatürk Street.
(literally: Dairem Atatürk caddesi üzerinde bulunuyor.)

-den/-dan case(ablative): This indicates our noun is subject to a departure.It indicates location and direction as well."From" is equally used in English.
ex: Okuldan geliyorum->I'm coming from school.
Karolina bana Stockholm'dan bir kartpostal gönderdi.
->Karolina sent me a postcard from Stockholm.