"Daniel then said to the guard whom the chief official had appointed over Daniel, Hananiah, Mishael and Azariah, 'Please test your servants for ten days: Give us nothing but vegetables to eat and water to drink. Then compare our appearance with that of the young men who eat the royal food, and treat your servants in accordance with what you see.' So he agreed to this and tested them for ten days." NIV translation
The number ten is associated with the earthly completion and divine order and so it is no coincidence that this was the period of time for the test that is described. This young man of faith (Daniel) simply trusted God and asked his guard to look at the results. We can have that same confidence if we pray and seek God's will for each of our steps in our daily life.
"At the end of the ten days they looked healthier and better nourished than any of the young men who ate the royal food. So the guard took away their choice food and the wine they were to drink and gave them vegetables instead." NIV translation
We see, here, that God took care of the men because they were obedient to His leading. It was obvious to the guard that God was taking care of them and so he showed them favor. The same type of thing can happen to any believer that is following the lead of the Holy Spirit. God can cause others to show the same kind of favor to us as well.
A saying that I have heard is: "If it's God's will, it's His bill" meaning we can trust Him to take care of us while we are following Him.
"To these four young men God gave knowledge and understanding of all kinds of literature and learning. And Daniel could understand visions and dreams of all kinds." NIV translation
The men, led by Daniel, were obedient to God and He raised them up by giving them knowledge. Daniel, as the leader, was given a special blessing as He could understand messages from God. This verse reminds us that (1) God uses children sometimes to teach us adults a thing or two about Him; (2) knowledge and wisdom for all things is a gift of God; (3) God rewards His obedient children.
"At the end of the time set by the king to bring them in, the chief official presented them to Nebuchadnezzar. The king talked with them, and he found none equal to Daniel, Hananiah, Mishael and Azariah; so they entered the king's service." NIV translation
At the end of their training period, they were brought before the king and found to be better than all of the others that had went through the training. So, they became the servants of the king. Although it may not seem like it, this was a blessing from God as they would have eaten better and had many other advantages over those that were not in the service of the king. That is a good example for us to remember as many times we find ourselves in positions that, at first glance, seem lowly but in fact are a blessing from God.