How are H1b taxed on wages? Can h1b visa holder entering the US in 2009 with her family claim herself and dependent on her withholding certifcates or must she only claim herself?

If the family is in the U.S. for at least 31 days AND they end the year being present in the U.S. then the H-1B visa holder can file jointly with his/her spouse and claim their children as dependents, and also qualify for the $1,000 Child Tax Credit for each child under the age of 17.