If you are due to accept an award it's best to prepare yourself in advance. When writing your speech, begin by thanking the organisation or persons who are presenting you with this award and explain what an honour it is for you to receive. To make for an inspiring and memorable speech, provide the audience with some context by giving them a brief summary of the work you underwent in order to achieve this award and why you decided to get involved in the first place. In order for the speech to captivate and connect with people, you could insert some witty anecdotes, but only if you feel comfortable in doing so. These could be based around the individuals you worked with, an embarrassing moment or perhaps a time when you struggled to complete your voluntary role. If you feel it's relevant you could insert a quote that has some significance for you. Remember to be genuine and humble, rather than boastful and use the time to thank anyone who helped you along the way, including an overview of how they helped. You may also wish to explain how being involved with this voluntary role has helped you in life. Before you attend the presentation, dress smartly, avoid drinking alcohol to excess, take long, deep breaths and sips of water. Some people find public speaking terrifying, but treat the audience as old friends, they're not there to judge you. Don't fret about reading your speech word for word as this may seem rigid on the night, but having a clear idea of what you want to say beforehand and practising will settle your nerves and increase your confidence, to ensure you deliver a memorable and concise speech that you can be proud of.
You could start out with a joke, or a question. You could also take the direct approach and start off with: "I would like to start off with saying a big thank you for this award". Tell the audience what it means to you to receive that award and personalize your speech.