Back in rural Alabama, when we served a summons and complaint, or a subpoena, or any other document that warranted service, we used the Sheriff's department. It was a one-step process: take the document to the courthouse (or e-file it), and let it go. The return on service would usually take around a week... if we were lucky.
I have since learned that private process servers are much more time efficient and focused on service of your specific documents to your specific defendant, deponent, or custodian of records. Within my first week at my Memphis job, I was introduced to the world of private process servers. The new system involves a couple more steps, but it takes much less time.
Step one: Send subpoena to court to be file-stamped and issued. Ask runner to return file-stamped issued subpoena to me for service.
Step two: Call private process server to come pick up subpoena for service.
Step three: Wait for return on service. The great thing about a private process server is that he or she will likely try more than once to perfect service, and if the address you gave is inadequate, will often put in some time finding a better one. He then usually takes the subpoena back to the court to be filed.
Every once in awhile, I am asked to issue a subpoena in another state, or several hours away from this county. In these cases, I realize how convenient it is to know local process servers.
I once had to arrange for issuance and service of a subpoena in a rural part of the great state of Texas. In this little town in the middle of absolutely nowhere, I looked for hours for a process server. I finally found someone to help us with service, but he was located nearly two hours away. Because we were in a hurry to perfect service, I overnighted the subpoena to the local court in Texas, then arranged to have the process server drive in from two hours away to pick it up at the clerk's office and serve it.
I did not know the Texas process server I used, but now I do. Just in case, you know, we ever have to issue a subpoena in Middle Of Nowhere, Texas again.
Many private process servers also include other services, such as copying and imaging, or private investigations. So knowing you local process servers could mean knowing your local PI and document imaging business. Because of the nature of the business, many of them also have various connections in your town or city that could prove useful in the future.
If you currently use the Sheriff's office as your main server of process, I would suggest considering a private server. They can be more expensive, but you may find that the added cost is worth the added benefit. At the very least, get to know a local process server, whether you believe you will use him for service or not. You never know when his connections, knowledge, or related skill set will come in handy.