It was said:
You must know who your Lord is so you can worship God properly. That is, your `Aqidah needs to be correct. This universe must have a Creator—for it could not have brought itself into being. Know that the Creator’s proper Name is Allah. Allah is One. No one is the Creator except Allah. Allah is beyond need or comparison. Allah has power over all the creations, and Allah knows everything—without exception. Allah knows what was, what is, and what shall be. Nothing is hidden from Allah. Allah has no size or shape. Allah is not an object and does not take up space. Allah exists without a place or direction, for Allah existed before direction and place, and Allah did not change after creating direction and place. Allah is not a “spirit” (or a soul)—but Allah is the Creator of the spirit. Allah is not light or darkness. Allah is the Creator of light and darkness. Allah is absolutely different from the creations. Whatever you imagine in your mind, Allah is totally different from that. For more on the Creed, my advice is to begin with the Creed of at-Tahawiyy. Memorize it and let its meaning grow in your heart.
Know that Allah sent Prophets. Prophets are men who received God’s Revelation. The Prophets are the best of all the creations. They were all men of the highest honor and dignity; they were all Muslims. The Prophets never worshiped anyone or thing other than Allah. The Prophets never-ever committed major sins (like, murder or fornication) and they didn’t commit minor sins that would indicate a lowness of character. Prophet Muhammad is the last and greatest of the Prophets. Learn about his life. Your salvation is based on following his example. And again, remember, the Prophets are the greatest of the creations. Do not dare ascribe anything unbefitting to them.
Also, be warned about apostasy and deviant factions and misconceptions. Apostasy means for a Muslim to commit blasphemy (/disbelief), that is, to believe, say, or do something that would terminate his Islam, such as, for one to think that Allah is a body, or that Allah is in a location or direction, or that Allah is literally everywhere. Likewise, treat the religious papers properly. Do not throw religious books or papers in the trash, or step on them. This is blasphemy. Do not help others in disbelief, for that is disbelief in itself. Also, be careful with your tongue. Weigh your words before you speak. The Prophet said most of the sins of humanity come from the tongue. Insulting Allah, the Prophets, the Holy Qur’an, the Angels and the like entails disbelief–whether one said those words with or without conviction or in a state of anger or delight. Claiming something is permissible when it is forbidden entails disbelief, such as, claiming that alcohol drinking is allowed in Islam. Do not belie the Religion. Even if one was joking, if one says a statement of disbelief, then he is not a Muslim.
As for deviant factions, in the big cities, the main group you will encounter are the so-called “Salafis” or “Salafiyyah Da`wah” (what are known to the Sunnis as the “Wahhabis”). These people pray to a giant imaginary unidentified extraterrestrial shadow casting object with a smiling face, fingers, one shinbone, and two feet. They aren’t Muslims. These so-called Salafis don’t pray to Allah—they pray to a figment of their imagination—and Allah is greater than whatever we can imagine. Remember: Allah is not a body, and Allah does not have a direction or place. Size, direction, and place apply to objects, and Allah not an object, or similar to an object, nor is Allah similar to any other creation. Also be warned of the so-called Nation of Islam and the so-called Nation of Gods and Earths (the Five Percenters). These people claim that the Asiatic Blackman is the Creator of the universe. God is Beginningless and Free-of-Need. How could the human being be the Eternal Creator of the universe, when the human needs the creations in order to exist? Also, be warned of the likes of the Ahmadiyyah/Qadianiyyah, who claim a new Prophet came after Prophet Muhammad. This is a blasphemous belief. And also, avoid the mass of “jailhouse Muslims” and other ignoramuses out there, who never took the time out to learn their religion properly. Because they are confused, they will only cause others confusion.
Among the greatest challenges you will face in the beginning of your journey is the difficulty in finding knowledgeable and trustworthy people. When you seek the knowledge, investigate and see what the teachers or imams say about the likes of Ibn Taymiyyah and Muhammad ibn `Abdul-Wahhab, or Ibn Baz, Al-Albani, or `Uthaimeen. If they praise these characters, then it is a good sign they are Wahhabis (so-called “Salafis”). Avoid them, like they had leprosy. Also, investigate and see if these teachers are educating the students about apostasy. If they are not informing Muslims about matters that would cancel a person’s Islam, it is a sign that either they are ignorant or they have some kind of ulterior motives. Be all the more warned about those people who are telling their students to learn about the matters of apostasy. In a society as infected with disbelief in God and the Prophets as America is, how could these people be telling their followers to learn about how to protect themselves from falling out of Islam? It is clear such teachers and “leaders” have an agenda—and their agenda isn’t to educate and protect the Muslims.
Of course, your studies will need to go beyond learning just the basic matters of the Islamic Belief, but as far as finding a teacher, if the teacher’s creed (`Aqidah) is not right, then he can’t be trusted in the other matters of the Religion, which are not as critical. I hate to sound partisan, but the only major organization that I know of teaching in the English language the matters of Creed, apostasy, and warning against the various deviant factions and misconceptions is the Association of Islamic Charitable Projects. You can find their website at aicp.org. I am not saying they are the only organization out there, but to my knowledge, they are the most careful and accurate organization out there in spreading traditional knowledge and warning about misguided groups by name.
 That is not to say that some of the Muslims who spent time in prison did not acquire the knowledge of the Deen, reform themselves, and come out as transformed human beings. I am talking about the mass of those ex-con Muslims who are ignorant and confused and speak in ignorance and misguide others.