You can claim either 0 or 1 on your W-4. It won't create problems with the IRS, it will just determine how much you'll get back on your tax return next year. If you claim 0, you will get less back on paychecks and more back on your tax refund.
A single filer with no children should claim a maximum of 1 allowance, while a married couple with one source of income should file a joint return with 2 allowances. You can also claim your children as dependents if you support them financially and they're not past the age of 19.