I have received a number of requests for volunteer placements and/or for support locating volunteer placements. The conversations more of less start off in the same way, summarized here for those in a similar position:
Getting started. Make sure you check out organizations that specifically place volunteers/interns to see if you might meet their criteria, such as VSO and CUSO. Many of these organizations are seeking candidates with specific qualifications, so if you are a student or recent graduate you may not meet their criteria. There are country-specific programs geared towards new graduates, such as this one in Canada. If those do not work out, or are not what you are looking for, you have to start the (sometimes difficult) search to find your own placement.
The world is a big place. You will also be in a better position to locate a placement if you have a particular geographic area in mind. If you are sending out unsolicited requests, make sure you include a brief biography. Organizations and people linking you to organizations will want to know a bit about you and what skills you bring as a volunteer (3-5 lines).
Look ahead. Rather than taking the first opportunity that arrives on your table, I suggest that you think about your goals. If you are going to volunteer for an extended period, you will gain cultural, linguistic and regional knowledge that will shape your area of expertise, and also you will build a network. You are not permanently limited by this choice, but future employers will value relevant experience. I have seen that employers increasingly value country-specific expertise rather than generalist experience/skills. Having said this, I suggest you take a moment to think about regions and languages of interest, and use that to specify your volunteer placement requests. This will also help narrow down your search for organizations.
As a student or recent graduate, you may not have the opportunity to determine the type of work you get involved with at this point. It is nonetheless worthwhile to think about. Are you interested in health policy? Food security? Monitoring and evaluation? Research? Empowerment? Education? Communications? Management? Supply Chain? This is something you should be thinking about, and building your knowledge (including additional trainings and certificates) and experience to guide your career direction.
Type of organization: Large organizations, with well organized volunteer placement systems, tend to offer experiences where you will be office-based in a capital city – frankly, a lot of international development jobs for expats are located in offices in capital cities. However, you might want to consider a less structured placement with a local/community-based organization. There will be less support, but you may have more opportunities to engage with community-based projects that are run on shoe-string budgets, and often managed by extremely passionate and grossly underpaid everyday heroes. Part of this will relate to your comfort level, as these resource-constrained community organizations will not offer you much support.
Time. If you are looking for a placement of several weeks or less, I suggest you reconsider. Wherever you go, you will drain resources – people will take you around, translate for you, provide you with direction, give you tons of essential background information and so on. In the first few weeks you are just getting settled, and will (with some exceptions) not be able to contribute to a project or organization in any significant way. You will probably benefit more than anyone else (here is one post worth reading). I think this is important to recognize, so you take along a greater sense of humility when you set out. If you are planning to use this volunteer placement as a means to beef up your CV and transition into paid employment, be aware that 2-6 week placements carry little weight, and short volunteer placements are more like adventures / tourism than work experience.
Be informed. Read up on international development (suggested books here) and follow the trends. Wherever you are going, read as much as you can about it so you are familiar with the culture, history, politics, challenges and so on.