if we owe more on our house then it is worth, what is the best way to vacate it legally

Unfortunately, there’s no one simple answer to your question.  The factors that play into it are numerous.  The options that are out there may range from packing up, moving out, and accepting the eventual foreclosure judgment with potential for a deficiency judgment to cash for keys, etc.  And watch out for non-lawyers pretending to be lawyers trying to give you advice.  I would highly recommend seeking the advice of a local foreclosure defense attorney.  To really know your options, you’re going to need to discuss the totality of your situation in a confidential environment.