You could invest in some live traps that will let you catch them alive but I would recommend getting a professional exterminator to come and do it for you. Expect to have them spray no matter if you do it or a pro comes to your aid.
You will need to trap the skunks and have them removed. Check if the local animal shelter will provide a skunk trap for your use. If one is caught call the local animal control for removal. You can also hire a skunk removal company. Check local businesses.
The only method that seems to be effective is to encourage them to move elsewhere. Supposedly a deep bass on a CD player annoys them enough to find new quarters.
Keep your yard less inviting to the skunks. Keep fruits and vegetables clear. Mothballs are known to have a displeasing effect on skunks so if you don't have children or pets around, sprinkle some in your yard.
