The Two Testimonies of Faith (Shahaadataan)

The Meaning of Laa Ilaaha Ill-Allah (the Shahaadah)
This is the phrase of Tawheed . For this concept, Allah brought the creation into being, and for this concept He created Jannah and Hellfire. Allah says:
"And I have neither created the Jinn nor humans except to worship Me." (51:56)
This is the belief which all Prophets and Messengers called their peoples to, from Adam to the last of them, Muhammad, may Allah exalt their mention and render them safe from every derogatory thing.
Allah says: "And we have not sent before you any messenger except that We have revealed to him that there is no deity that is worshipped in truth except Me, so worship and obey Me." (21:25)

The Meanings of the Shahaadah
The first testimony, that none has the right to be worshipped but Allah, includes the following meanings:

•  Allah is the One Who deserves to be worshipped. Allah says: "No doubt! Verily, to Allah belongs whosoever is in the heavens and whosoever is in the earth. And those who worship and invoke others besides Allah, in fact they follow not the (Allah's so-called) partners, they follow only a conjecture and they only invent lies." (10:66)

• Allah is the Creator of all that exists. Allah says: "Such is Allah, your Lord! Laa ilaaha illa Huwa (none has the right to be worshipped but He), the Creator of all things. So worship and obey Him (Alone), and He is the Wakeel (Trustee, Disposer of affairs, Guardian, etc.) over all things." (6:102)

• Allah is the Proprietor of all that exists, and the Disposer of all affairs. Allah says: "Surely, His is the Creation and Commandment. Blessed be Allah, the Lord of the ‘Aalameen (mankind, Jinns and all that exists)!" (7:54)

• To Him belongs the beautiful names and perfect attributes. Far removed is He from every imperfection. Allah says: "And (all) the Most Beautiful Names belong to Allah, so call on Him by them, and leave the company of those who belie or deny (or utter impious speech against) His Names. They will be requited for what they used to do." (7:180)

The Conditions of the Shahaadah
It is not enough to merely utter the Shahaadah for it to be accepted by Allah. It is a key to the gates of Jannah, but in order for the key to work, it needs to have the right notches.

The Shahaadah must meet the following conditions for it to be accepted by Allah:

1. Knowledge: Comprises knowing that all things worshipped besides Allah are false. There is no god worshipped in truth except Allah, even if it be a prophet, a messenger or an angel. Allah is the only One Who deserves all types of worship, such as prayer [Salaah], supplication (du‘aa), hope, sacrificial slaughtering, making oaths, etc. Whoever assigns any act of worship to other than Allah while that person intends to worship or aggrandize the one who he assigned it to has committed kufr , even if he uttered the Shahaadataan.
2. Certainty: The heart must be firmly certain of the meaning of the two Shahaadah. Certainty is the opposite of doubt, so there is no room for a person to doubt or waver in his belief. Allah says: "The believers are only those who have believed in Allah and His Messenger, and afterward doubt not, and strive with their wealth and their lives for the Cause of Allah. Those are the truthful." (49:15)
3. Acceptance: One should accept the Shahaadah fully, and not reject it. Allah says: "Truly, when it was said to them, “Laa ilaaha ill-Allah (no deity is worshipped in truth except Allah),” they puff themselves up with pride (i.e. deny it)." (37:35)
4. Submission, obedience and acting upon all what the Shahaadah necessitates. A person must do what Allah ordered and abstain from what He prohibited. Allah says: "And whosoever submits his face to Allah, while he is a Muhsin (doer of good) then he has grasped the most trustworthy hand¬hold [La ilaha ill-Allah]. And to Allah return all matters for decision." (37:35)
5. Truthfulness: One must be truthful in professing the shahaadah. Allah says: "They say with their tongues what is not in their hearts." (48:11)
6. Sincerity of worship: One must sincerely dedicate all acts of worship to Allah alone. Allah says: "And they were not commanded except to worship Allah, following the religion purely and sincerely for Him, turning away from other religions." (98:5)
7. Love: One must love the shahaadah and all that it necessitates. He must love Allah, His Messenger, and His righteous slaves. He must hate and show enmity towards all who show enmity to Allah and His Messenger. He must prefer what Allah and His Messenger love, even if it is differs from his desires. Allah says: "Say: If your fathers, your sons, your brothers, your wives, your kindred, the wealth that you have gained, the commerce in which you fear a decline, and the dwellings in which you delight… are dearer to you than Allah and His Messenger, and fighting in His Cause, then wait until Allah brings about His Decision (torment). And Allah guides not the people who are Al-Faasiqoon (the rebellious and disobedient to Allah)." (9:24) The Shahaadah also necessitates that Allah is the only One Who has the right to legislate, whether it be in matters concerning worship or those concerning human relations, in both individual and public matters. The act of making something prohibited or lawful is for Allah alone. His Messenger (peace be upon him) merely explained and clarified Allah’s commandments. Allah says: "And whatsoever the Messenger gives you, take it, and whatsoever he forbids you, abstain (from it)." (59:7)

Source: http://www.1ststepsinislam.com/en/two-testimonies-faith.aspx#conditions