Ok, since it seems that you are new to this, I will need for you to read at least the basics on how to overclock your CPU. I cannot just tell you to raise or lower a value because if something goes wrong you might fry the CPU/board or both. http://www.tomshardware.com/forum/240001-29-howto-overclock-quads-duals-guide
the guide is pretty strait forward and there are many examples of what is needed even for a small overclock. I also assume that you are using the stock CPU cooler. If you are going to do any overclocking at all it is important that you monitor your temps using a 3rd party software :http://www.techpowerup.com/realtemp/
In your case you should be able to get at least 3Ghz with the stock Intel cooler. If you are looking for a more agressive overclock you will need something like this :http://www.newegg.com/Product/Product.aspx?Item=N82E16835207006&cm_re=core_contact_freezer-_-35-207-006-_-Product
Your temps will depend on your case, airflow, cable management and ambient (room) temp as well.