Voter Registration -- Voter registration was essential because the more votes you have the more of an impact you can have on the existing system. "The vote is not a guarantee of change in policy but it does increase the probability that certain race goals can be accomplished."
Boycotts -- Boycotts were an effective means of protest because the hurt the system where it hurts most, in its wallet. By coordinating an entire segment of the population into not buying merchanddise from a specific retailer or buying a service you can really have an effect. It works because you make the merchant lose money.
Sit-Ins -- Sit-ins were another effective form of non-violent protest. Having a presence in a specific locale or business can arouse sympathy for the cause. They also cause an inconvenience for the business. The original Greensboro Woolworths sit-in triggered a flood of other sit-ins across the South. It also sparked a sympathy boycott of Woolworth nationwide.
Marches -- Marches were a great tactic for arousing public opinion and sympathy. They also served to get people from all over involved in the movement because all you really had to give was your time and yourself. Getting people together in a march was also great for morale. Also, depending on the turnout, media coverage got the message out to millions more people.