"Then Ehud drew the sword from his right thigh with his left hand and plunged it into his belly."
To do what Ehud did mentioned at Judges 3:21, he had to have a lot of courage. Today we also need courage to carry out our ministry, especially if we face someone intimidating. If we want to develop courage we need to regularly study the Bible because knowledge builds confidence. Prayer will also help us because God's spirit will help us say the right thing in the proper way. But, ultimately Ehud succeeded because he had God's backing.
You can read the Bible online for free at JW.org