There are alternatives to starting an NGO - in some cases more valuable and more effective than starting your own NGO. Here are some offered by About.com:

• 1. Seek fiscal sponsorship from an existing NGO
• 2. Volunteer for a nonprofit that is doing something similar to what you have in mind.
• 3. Start a local chapter of a national non-profit.
• 4. Put together an unincorporated association to fulfill your mission without seeking tax-exempt status.
• 5. Form or join a giving circle.
• 6. Set up a donor-advised fund which makes grants to charitable causes of your choice.
• 7. Become a social entrepreneur by forming a for-profit social venture to accomplish your social goals.
• 8. Organize support for a cause at an online social networking site.

Advantages

Volunteering for an NGO, or getting heavily involved in fundraising, give you the chance to learn the ins and outs of the situation before you try to run something yourself.