The National Association for the Advancement of Colored People (NAACP) was the preeminent civil rights organization in the United States up through the Brown v. Board of Education decision in 1954. After that, however, it lost some of its importance. This happened because the NAACP chose a strategy of litigation and, later, lobbying, that lost favor as African Americans and their allies turned to direct action as a strategy.
After WWII, the NAACP and its Legal Defense Fund waged an offensive against Jim Crow laws in education. They chose to use litigation as their main weapon. They filed lawsuits against various universities to try to break down the Jim Crow system at that level. They felt that it would be easier to start at that advanced level to get their foot in the door before attacking segregation in K-12 education. Their strategy paid off with the Supreme Court’s decision in Brown.
After Brown, however, the NAACP became less important. Other groups, such as the Southern Christian Leadership Conference (SCLC), led by Dr. Martin Luther King, Jr., became more prominent because they supported direct actions such as sit-ins and protest marches. The NAACP did not support these actions and so fell out of prominence.
The NAACP did continue to be somewhat important in a more behind the scenes manner. It continued to lobby for laws such as the Civil Rights Act of 1964. However, it was no longer the most important civil rights organization.
So, we can say the NAACP chose litigation and, later, lobbying, as its strategy for promoting civil rights.