Jonathan offers excellent advice.
I'd just add a caution that simply increasing your offer by a certain percent isn't always safe or best. Make sure you know what the house is actually worth. Some foreclosures are good buys. Others aren't. I did a real quick search of some townhouses under contract in 20147. These all appear to be short sales, some possibly REOs.
List price: $229,900. Described as "needs work." It sold for $300,000 in March 2004.
List price: $259,000. Sold for $281,000 in January 2004.
List price $259,000. Sold for $259,000 in July 2003.
List price $259,900. Sold for $350,000 in January 2006.
Youngster: These are not bargains. I can find you plenty of properties that sold for $300,000 in 2006 that are now listed for $150,000. Or properties that sold for $500,000 in 2006 that are now listed for $325,000.
I also took a look at recently sold properties, both short sales and "regular" sales. There's no real bidding wars going on that I could see. It's possible, as Jonathan implied, that your offers weren't as strong as those that were accepted.
But don't chase properties just because they're REOs or short sales. Pursue properties that offer genuine values. They're not difficult to find. And you won't have to go through the additional hassle that's involved in an REO or short sale.