Honestly, if you want to do it healthily slow and steady is the way to go. I wouldn't rush yourself like that.
But there are some things you can do to just lose the most weight as you can. Eating veggies, fruits, salads, etc. Exercising, too.
And, really, 20 pounds in less than a month? You'd have to lose 4 pounds a week for 5 weeks. I'd really be careful about this. You're trying to lose 20 pounds in a month, when it would take others many more MONTHS to do it the healthy way. I'm not saying it's impossible, just risky.