When you have concluded, discipline yourself to stand perfectly still. Select a friendly face in the audience and look straight at that person.
If it is appropriate, smile warmly at that person to signal that your speech has come to an end.
Resist the temptation to:
Shuffle papers.
Fidget with your clothes or microphone.
Move forward, backward, or sideways.
Do anything else except stand solidly, like a tree.
Take a look at this video of how I ended a speech when I received an award from the National Speakers Association. I ended this speech exactly how I described here.