the water hose? put a washer in the female end, or replace the hose.

for the hose bib itself, you can either repack it, or replace it. sometimes it helps just to tighten the nut. look right under the handle, you will see a nut around the handle. tighten this a little and see if the drip stops.

if you replace the hose bib, turn off the main supply to the house, remove the bib, then put some fresh teflon tape or pipe dope on the threads of the nipple from teh wall, and screw on the new bib. then turn ont eh main supply and check for leaks.

no need to call some one in for either item.