I just learned how to do Kongs JUST HOURS AGO..... so I can give you a tip as how I did em. Try looking down, have you head facing the object you are vaulting over, and run fast, I noticed speed helps when you dive.
But as I learned how to do Kongs just Hours ago, don't take my advice too seriously, that video Andy posted seems to be a good resource to learn from.
Also remember, A kong vault is basically a Diving Monkey Vault, Learn how to Monkey Vault and a Kong will be that much easier.