In the material settings, under the render pipeline section, there is a button called 'strands' in grey. click that and a mini-menu pops up where you can fiddle with width and shape of the strands.
to get really good looking hair particles you will want to add an alpha blending texture to the material to fade out the tips and give a nice anti aliasing effect.
Also you can switch from object/edit mode to particle mode and press n to bring up a particle properties menue in the viewport. it'll let you comb, style, cut, grab and move etc the hairs individually or with a brush.