Making Promises to God

Is it ever right to make a vow to God so that He might grant our request? In Judges 11, Jephthah makes a very foolish vow to God. Clearly it was unnecessary. But what can we learn from him about making vows to God? (And by the way, did he really offer his own daughter as a human sacrifice to keep his vow? Why would the author of Hebrews hold a man like Jephthah as an example for our faith in Hebrews chapter 11?)