Pace yourself - busy day, not so busy day, and try to use the transport rather than walk everywhere. It's easy to do a 12 mile day, but you'll end up paying for it. Food is expensive, so budget for it. Most NY restaurants have wrbsites to give you an idea of prices - and they expect a 15% tip...
We went ove rfor the second time in May. Do the boat trip that goes half way round the island - it takes in going round the statue of liberty and under the Brooklyn Bridge. Don't bother with going to the statue itself as you will spend hours being herded in a cowshed for security checks and...