Allah SWT has mentioned in Quran: 

أَوْزِدْعَلَيْهِوَرَتِّلِالْقُرْآنَتَرْتِيلًا 

"Or a little more; and recite the quran (aloud) in a slow, (pleasant tone and)style." [1] 

This shows that Allah SWT wishes us to recite Quran not only correctly, but also beautifully. We all know that reading and reciting is a good deed that would be weighty in our scales on the Day  of Judgement. But do you know that the correct pronunciation of every word is also important? Even the slight mistake in pronunciation can change the entire meaning of the text, and it may become a sin, instead of a good deed.

The rules of correct pronunciation of Quran are known as tajweed. It is essential to learn the reading and recitation of Quran according to the rules of tajweed to earn the Pleasure of Allah. Although learning correct tajweed is not fardh (obligatory), yet it does have the status of Mustahib( Much preferred).

Tajweed involves the correct use of emission points, or Makahrij; the points from where the letters are pronounced. According to the scholars, there are five main points which makes way for 17 Makahrij. 

1.          JOFF: The area between chest and the mouth. It makes one makhrij, and is used in pronouncing three letters.

2.          HALAQ: This includes the throat area. It makes three makharij, and is used to pronounce six letters.

3.          LISSAN: It means the tongue. It makes ten makharij, and is used to pronounce eighteen letters.

4.          ASH-SHIFTAN: It means the lips. They make two makharij, and are used to pronounce four letters.

5.          AL-KHISHOOM: It includes the internal area between nose to mouth. It makes one makhrij, and is only used to pronounce ghunna.

It is always a good idea to start learning how to read Quran with correct tajweed by using  Noorani Qaida. It has been specially created to not only teach the students the correct tajweed, but to give them practise, too. "Practise makes the man perfect," is indeed true in case of learning and practising correct tajweed. Noorani Qaida is equally good, if you are trying to improve your tajweed skills. Noorani Qaida is the easiest way to learn tajweed, however, there are several other books of tajweed that can be used and benefitted from.

While learning tajweed, you need a good teacher, too. Without a good teacher, you just wouldn't be able to perform well. Tajweed rules cannot be just learnt while seeing them in print. You need to hear the proper pronunciations, see which Makahrij to use for different Arabic alphabets; only then can you learn better tajweed. If you are trying to learn Tajweed online, you can use different pictures, or videos, to learn the different points of emission, to get a better grip at tajweed.

If you have issues in finding a good teacher, try learning tajweed online. An online Quran teacher of a reputable institute is usually selected on a strict criteria. The teacher is qualified, trained, and experienced in imparting correct tajweed and assist in learning Quran. Online Quran teacher is much more advantageous choice than regular Quran teachers; You can learn reading and reciting Quran with ease while sitting in your home; You can save time that you would otherwise had spent in commuting to and  fro from home to your institute; You can save the amount you would have spent on fuel otherwise; You can learn on your own personal pace; You can choose between group classes or personal classes, too. The best of all is that you are not going to compromise on quality while achieving all of this.

There are 28 basic alphabets is Arabic, 29 if we include hamza, too.

 ابتثجحخدذرزسشصضطظعغفقكلمنہوي

These letters are divided into two main groups.

Lunar or Qamari Alphabets

Solar or Shamsi Alphabets

It was narrated by Qatada:

Anas(RA) was asked, "How was the recitation(of the Quran) of the Prophet(SAW)?' He replied, "It was characterised by the prolongation of certain sounds." He then recited: In the Name of Allah, the Most Beneficent, the Most Merciful prolonging the pronunciation of 'In the Name of Allah, 'the most Beneficent,' and 'the Most Merciful.[2]

This hadith clearly indicates that we need to read Quran not only with correct tajweed, but we also should try to beautify our voices while reading and reciting Quran. We should pronounce each letter correctly; not prolonging it without requirement, nor pronouncing it hurriedly.

According to the scholars, there are three speeds for reciting or reading Quran.

1.      TEHQEEQ: Pronouncing every letter while using correct Makharij.

2.     TARTEEL: Pronouncing every letter while using correct Makharij, while keeping in mind all other rules of MADD, GHUNNA, TAFGHEEM, TARQEEQ. This is the most desirable way to recite Quran.

3.     HADAR: Recite Quran at a fast pace, like that of in taraweeh, bearing in mind all the rules of tajweed.

References:

[1]Chapter 73, Al-Muzammil, Verse 4

[2] Narrated by Sahih al-Bukhari, Hadith  5046