You have to treat those that you are about to give orders to with respect. Talking to them in a way that you would want to be talked to is key to showing them that you are respecting them yet you are their boss or manager.
First off don't give out ORDERS. Talk politely to others so they will respect you and they will see the same from you. Call them instructions.
Give out tasks with a clear direction so that they know what is expected of them and let them know if they have questions to feel free to ask you. That way if there is any confusion they know they can come and talk to you rather then just ignoring doing the task.
Be a leader. Make sure that you are not being their "friend".Many may take advantage of their friend and not see them as a manager. So make sure that they know business is business.
The same work is expected of everyone! Do not play favorites.
When they are doing a good job let them know it. Just letting them know that you are aware of their progress will give them a sense a pride in their work.
When you are in charge it is your duty to make sure that things get down. However you can not do everything by yourself. So delegate duties properly to the ones that are there to help you. Allow them the freedom to perform the task and do not stand over them and expect it to get down. That will create a unwelcoming environment for you in the future.
In the position myself when I was a manager I know how hard it may be at first to start giving out instructions to others. So just know that it is your job to oversee certain things get done and if it is not done properly then you will be the one to blame.
So delegate tasks out to the ones that you think will be best at the certain job or rotate them to ensure everyone gets a chance at something different. I just know that the saying stands true when asking others to do a job and that is TREAT OTHERS AS YOU WISH TO BE TREATED!