At Home Depot & Lowe's you can find a long plastic strip with plastic teeth on it which is very helpful for cleaning sink drains. It costs less than $3 & is called a Zip It Bath & Sink Snare. Here is the link.
http://www.homedepot.com/Plumbing-Dr...&storeId=10051
I have used it very successfully for removing hair & grease from sinks & if your probem is more difficult to resolve, you've only spent $3.