Unfortunately, I do have to play of the devil's advocate a little bit here:
This is a repeat of a previous comment I have med in regards to volunteering overseas. I currently live and work in Cambodia. A lot of people want to come to places to help which is awesome but it is not as easy as showing up with a first aid kit.
You really need to do your research on this. It is not easy to just come over here and help even though the need is high in some areas.
If you don't speak the language or understand the culture it is near impossible. Often by starting to help then leaving it causes more harm than good unless you are helping to empower the locals and make the project/organisation sustainable.
Look into places that get you to come and teach/train staff instead of trying to help the local people yourself. By increasing the knowledge of local people that are already doing good work you will help a lot more.
If you do decide to volunteer with an organisation make sure it is reputable. Don't volunteer at orphanages, most of them are shady.
Have a look at this video. Documentary 'The Voluntourist': Is voluntourism doing more harm than good? - YouTube
it was made by people I know here in Cambodia and gives you some insight into what voluntourism is and the effects it can have.
At the end of the day, if you want to come to these countries it often is better to come and have a holiday and spend your money on organisations and places that already have a good sustainable structure in place. There is a lot of them around that are doing really good stuff. So by you buying their products or services this actually makes more of a difference.