When you visit a country, especially if it's in the developing world, often you can't forget what you've seen - and want to give back to a community. Volunteering is an increasingly popular ways for travellers to express that desire.

But if you're not careful about how you spend your money or where you volunteer, despite every good intention you could end up hurting the people you're trying to help. A 2010 study explores how 'voluntourism' - specifically relating to travellers  providing short-term volunteering as caregivers to 'AIDS orphans' in sub-Saharan African - can negatively affect the children, not to mention encourage profiteering from orphanages.

The problems are many, writes Ian Birrell in The Guardian: 'Wealthy tourists prevent local workers from getting much-needed jobs, especially when they pay to volunteer; hard-pressed institutions waste time looking after them and money upgrading facilities; and abused or abandoned children form emotional attachments to the visitors, who increase their trauma by disappearing back home.'

This doesn't mean you shouldn't volunteer - it just means that you should arm yourself with the right information so you can volunteer in a positive way. So what questions do you need to ask? We spoke with Karen Leonard, founder of Lifestart Foundation in Hoi An, who gave us some great practical advice:

Do your homework. 'What we want is for travellers to be informed. That way they can make decisions with the head rather than the heart once on the ground. Otherwise, they can be swept up by a tide of emotion. I used to buy the Lonely Planet guide a year before landing in the destination. It's the same thing with volunteering. It's not uncommon for our volunteers to prepare six months ahead for a two-week stay. So read up beforehand and make that part of your study. That way you can go with a plan rather than an impulse.'

Choose the right organisation for you. 'Research organisations first rather than walking in off the street. Read their website and ask yourself: is that the kind of philosophy I want to align with.'

Check an organisation is legitimate. It can be really hard to tell from afar whether an organisation is reputable or not. 'One of the best ways is to check the organisation's credentials,' says Karen. 'Make sure that they're registered in their country of origin and that they're registered with the local government.' Lifestart Foundation also requires police checks for volunteers, another indicator of an organisation seeking to protect the people it's looking after.

Contact the organisation before going. 'Don't just drop in, email the organisation beforehand,' recommends Karen. That's better for everyone. 'That way organisations can provide you with useful pre-departure information and information for when you land in a country. And you can find out in advance what hoops you need to jump through before landing - for example, you can't get a police check once you're in country.'

Ask the organisation what they need. Rather than superimpose your skill, ask what the charities need. Dream volunteers, says Karen, are 'the ones that say "I've got two arms, what do you want done?" Basically,  daily, hourly we don't know what our needs are going to be. We had a flood last week and just needed people to shovel mud.'

If you can only volunteer for a short time, check that this makes sense. Most organisations would prefer longer term volunteers, says Karen. Otherwise, 'by the time we do a short-term induction...the week's over.' That said, some organisations will be able to use even one or two days of help.  Longer term is probably anything from a 3-month placement up.

Make sure volunteering is the best use of your time. What if you don't have the time to volunteer - but still want to give something back to the community? Why not do some fundraising beforehand, suggests Karen. 'Seek out a charity where you're going to donate and contact them beforehand - see if they need anything brought over. That way you can do something very direct like a quick whip around at work before you go.'

Think about where your money is going. 'Sometimes places can be kept looking poor so people delve into their pockets. But that money never goes to the children - or the improvement of an orphanage. The kids are just used as a pawn in this.'

Finally, always ask yourself this question when volunteering. 'If it was your child, grandchild, brother or sister in that situation, what kind of volunteering would be ok/not ok?  There are so many people who want to spend an hour at an orphanage,' says Karen. 'People take fluffy toys - and lollies - and go and kick a ball with the kids.' But often this constant stream of people is of little benefit to the children - and creates a situation in which they're just another sight on the tourist trail.

Despite the need to be careful about volunteering, Karen says she's incredibly inspired by volunteers, particularly from younger generations. 'I find more and more that young people are doing it earlier and earlier. It's quite natural to do it in your forties and fifties but I find it quite incredible that young people want to do it earlier at a peak time for their careers back home.'

For Karen, starting Lifestart Foundation in Vietnam was a natural conclusion to a life of travelling. 'I was always shocked by the disadvantage I saw but after returning home always got back into the groove of my normal life. But you get to an age where your children have grown and you think I don't have to just be shocked about this now, I can do something about it.'

Karen Leonard is the founder of Lifestart Foundation, an organisation aimed at helping disadvantaged people in Hoi An become self-sufficient. She says that one of the best things to do in Hoi An is simply to drink a Vietnamese coffee on a plastic stool on Bach Dang St overlooking the river. For about 30c you can feel the pulse of the city; a great way to start the day...

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