1) Make your schedule - a lot of agencies are short handed and would love if you could work 24 hours a day so let them know your availability.
2) Be punctual - volunteering is just like a job but you're not on the payroll plus they may have something for you to do that is time sensitive (like serving meals to the homeless).
3) Dress appropriately - if you are going to be outside wear suitable clothing for the weather and climate.
4) Be considerate - work at the job you were assigned and report to the team leader or volunteer coordinator if you want another task. Try not to just start helping someone else unless you ask them, they ask you or you are assigned to the task.
5) Have fun - the best thing about volunteering is the relationships you build. I worked with a broker who built his whole business off volunteering in the community. Also, the feeling you get from giving is priceless!!!
Now you are ready to volunteer in your community where you can make a difference....... and you'll be glad you did.