What aspects define a "true Muslim"?

Righteousness is not that you turn your faces toward the east or the west, but righteousness is [in] one who believes in Allah , the Last Day, the angels, the Book, and the prophets and gives wealth, in spite of love for it, to relatives, orphans, the needy, the traveler, those who ask [for help], and for freeing slaves; [and who] establishes prayer and gives zakah; [those who] fulfill their promise when they promise; and [those who] are patient in poverty and hardship and during battle. Those are the ones who have been true, and it is those who are the righteous. Quran 2:177