After he had finished all his sayings in the hearing of the people, he entered Capernaum. Now a centurion had a servant who was sick and at the point of death, who was highly valued by him. When the centurion heard about Jesus, he sent to him elders of the Jews, asking him to come and heal his servant. And when they came to Jesus, they pleaded with him earnestly, saying, “He is worthy to have you do this for him, for he loves our nation, and he is the one who built us our synagogue.” And Jesus went with them. When he was not far from the house, the centurion sent friends, saying to him, “Lord, do not trouble yourself, for I am not worthy to have you come under my roof. Therefore I did not presume to come to you. But say the word, and let my servant be healed. For I too am a man set under authority, with soldiers under me: and I say to one, ‘Go,’ and he goes; and to another, ‘Come,’ and he comes; and to my servant, ‘Do this,’ and he does it.” When Jesus heard these things, he marveled at him, and turning to the crowd that followed him, said, “I tell you, not even in Israel have I found such faith.” And when those who had been sent returned to the house, they found the servant well. (Luke 7:1-10, ESV)
As Jesus commends this man's faith, when he's more often pointing out a lack of it, we should pay close attention to what this man's faith is like.
Firstly, his faith starts with humility. Although the Jews describe him as someone who is worthy to have Jesus help him, the first thing out of his mouth (via his messengers) is "I am not worthy to have you come under my roof". He does not think Jesus owes him anything. He recognises his humble position before Jesus, despite being a powerful man in the world's eyes.
Secondly, he believes Jesus has absolute authority. His faith consists of not a hyped up confidence that Jesus will do it, but a confidence that Jesus can do anything and a humble request.
Do you want your faith to grow? Consider Jesus - your confidence in him will automatically grow.