Before you design a website for a non-governmental organization, you need to understand its purpose. Like any other organization, a NGO may have multiple uses for its website, including to solicit funding, to build a rapport with members, to state its position on a controversial issue or to share information. Creating an attractive website is important, but it's only part of the job. The website has to serve the organization's purposes and help it accomplish its goals.
Ask the NGO's representative how the group intends to host the website: It might be on its own server, a paid hosting service or a hosting company donating free service space. If the hosting is free, it may be bare-bones to the point it won't support CGI and other special features, so take that into account in your design.
Identify the audience the NGO wants to reach. If the organization's online goal is to attract donations, it needs a website that explains why it needs money and what the donations will be spent on. If the website's purpose is to connect with people who need help -- families who can't afford food, for instance -- it's more important to post a map showing local food banks, or instructions on applying for federal food aid.
Build the website to suit the NGO's goals. A good website focused on fund-raising, for instance, looks serious and professional, provides enough history, testimonials and information about the organization to show that donations are well-spent and should provide a link for easy donations by PayPal or credit card. A website for abused spouses makes vital information, such as shelter locations or a contact number for help, easily available and minimizes flashy, distracting elements.
Design the site so that it's easy for the NGO to make changes and updates. Unless you're a member or a volunteer for the group, the NGO staff will have to keep it running after you finish the job. The easier it is to post new information to the site, the better for the NGO and the people it helps.