Write a gripping first-sentence with something that will get the audience's attention immediately. Ask a thought-provoking question, say something controversial, quote somebody famous or tell a joke. As long as you make it relevant to the speech, it will undoubtedly grab them. If you can get the audience's attention immediately, you'll keep their attention for the duration of the short speech.
Establish a theme for the speech. Because it is only 10-minutes long, everything else that develops must tie directly into it. For example, if the theme is someone's promotion or the welcoming in of a new CEO, make sure everything else discussed has to do with that promotion or that new CEO.
Develop an outline for the body to the speech, bearing in mind it is only 10 minutes in length. List only the most important points or issues, keeping them to no more than five. Organize them in the order in which you'll speak about them. Allow each point to build on the other. For example, if you're speaking about a goal to be accomplished, speak first about the thinking behind the goal and then about the action-steps needed to achieve it. Tie it in ultimately to the speech's theme.
Expand the outline and the bullet points, turning sentences into paragraphs and expanding outward from there. For example, if you've bulleted "Contributions to the team goals," be sure to expand upon only the parts that apply to the theme of your speech, which in this case would be the individual's existing or upcoming contribution to the team's goals--and know what those goals are.
Write a closing for your speech. Summarize the speech's theme and recap what was said overall. Add a little more insight if there is time, such as another welcoming sentiment from a team of others or a quote from someone famous.
Read the speech aloud once to yourself in front of a mirror. Practice looking up at yourself, as you would the audience. Most of all, be sure you speak it in the allotted time frame of 10 minutes.
Read your speech to at least one person, but preferably two or three, to get feedback on its appropriateness. Get feedback on any grammatical errors, anything awkward sounding and staying within the time frame.