Every small business owner who makes hiring decisions makes mistakes. No matter how rigorous your screening and interviewing process, what you thought you saw is not always what you eventually get.
During the "new hire honeymoon period" it's easy to miss the signs a new employee won't work out as well as you hoped, especially since newly hired employees typically start a new job at the top of their games. In terms of attitude, effort, and enthusiasm, you usually get the very best a new hire has to offer.
That's why any problems that do surface during the first days are usually the tip of the poor-performing-employee iceberg.
Here are ways to tell almost immediately that you may have made a poor hiring decision:
Take me down to social media city*: Most employees assume Facebook, Twitter, and Internet access for personal reasons are a given, and almost every employee takes a little time out of their day for non-work inter-webbing. Still, when you catch a new employee during non-break periods, say, updating their Facebook status (especially if the new status is, "Why am I working here?") you can feel sure personal social media time will only increase in the future. A solid work ethic is established over time; a poor work ethic can be spotted almost immediately.
The lights are on but no one's home: An employee who is late or absent within the first few weeks will often be a chronic attendance offender. I once analyzed attendance records for over 1,000 employees over a five-year period and found employees who were late or absent in the first week of employment had a 35% likelihood of violating attendance standards and a 45% likelihood of lingering, for years, within one or two absences of violating standards. While there are certainly exceptions, the employee who misses one day early on typically misses a lot of days later.
"I would, but...": Most people a new job assuming the resources provided are the resources necessary (or simply available), and will only ask for additional tools when justified. (How do you really know what you need until you fully understand your job?) The employee who instantly needs a better computer, different desk, specialized software, etc. will tend to find external reasons why their performance is poor instead of looking inside themselves.
Assertiveness-squared. While new employees should definitely voice their opinions, raise concerns, and stand behind their reasoning and decisions, they should also take it slow and feel their way through interpersonal and organizational dynamics so they can build positive relationships. A new employee who takes too strong a stand, argues too loudly and long, or even borders on confrontational is likely to be a handful once the new hire honeymoon period is over. Quietly assertive is good; loudly assertive, especially in the first few weeks, means you may have hired someone who will always be a real handful.
"Here's what we used to do...": New employees should bring skills and experience from previous positions. But no one wants to hear how a previous employer did things, especially when a previous employer allegedly did those things better. An employee who frequently says, "When I was at my old job we used to..." has not made the mental transition to your business. Watch carefully for signs they continue to struggle with that transition; you don't want your business to be their rebound business.
* With apologies to GNR.