The first ninety days of a job are usually described as a trial for the new person. That is half of it. The other half is the employer finding out whether the job they advertised is the job that exists, and whether anyone actually has time to train someone into it. Both parties are on trial, and only one of them typically gets told so.
Worth clearing up first: in almost every state, employment is at will, meaning either side can end it at any time for almost any reason. A probationary period does not create a right to be kept after it ends, and it does not remove one during it. What it creates is a schedule of conversations. That is its entire value, and it is more than it sounds.
Week one belongs to you, not to them
The most common failure is not a bad hire. It is a good hire dropped into a week where nobody was free to explain anything, left to shadow whoever was least busy, and quietly written off by day forty for not picking things up.
Block the time before the start date. Who is showing them what, on which day, for how long. If nobody can commit to it, move the start date rather than burning the hire. A week of proper training is cheaper than replacing someone in March.
The conversation at day thirty
Fifteen minutes, scheduled, in the calendar from the first day so it does not feel like a summons. Three questions, and you ask them in this order.
What is taking you longer than you expected. What have you seen us do that made no sense. What do you still not know who to ask about. Then you say the one thing you want changed, specifically, with an example, and the one thing they are already doing well.
The middle question is the valuable one and the one most owners skip. A person thirty days in can see everything the rest of you stopped noticing years ago, and after ninety days they will have stopped noticing it too. That window closes and does not reopen.
The note at day sixty
Anything that will matter at day ninety has to be in writing by day sixty. Not a formal warning necessarily, and not a file full of grievances. A short email after a conversation, saying what you discussed and what you agreed, sent to them.
Two reasons. If it ends badly, a record showing the person was told clearly and given time to fix it is the difference between a clean parting and an argument you will lose the memory of. And if it ends well, you have a written record of what improved, which is the fairest possible basis for the raise conversation later.
If by day sixty you have nothing worth writing down, that is itself the finding. It usually means nobody has been paying attention, and the honest response is to restart the clock rather than pretend the period ran.
Three outcomes, not two
Most people treat the end of probation as pass or fail. There is a third, and it is the most common honest answer: the person is fine and the job is not what you described.
Someone hired to do installs who has spent ninety days answering phones has not failed anything. Neither have you, necessarily, if the work shifted. But saying so out loud, changing the description, and adjusting the pay to match is a real outcome and it keeps people. Pretending the original job still exists is how you lose someone in month seven and never understand why.
If it is a genuine no, say it plainly and quickly, on a scheduled day, with the final pay ready. Drawing it out helps nobody, and word travels in a small trade.
The thing to stop doing
Do not let the ninety days end silently. A probationary period that simply expires, with nobody saying anything, teaches the new employee that reviews here are decorative and that nothing they were told in week one was serious. It also wastes the only moment in the relationship where a frank correction is easy to give and easy to hear.
Put the date in the calendar the day they start, and put it in theirs too. Ten minutes on a scheduled day, ending with a sentence that names the outcome out loud.
What the ninety days leave behind
Run properly, the period gives you a written description of the job as it really is, a list of the things new people find confusing, and a person who knows exactly where they stand. All three are useful the next time you hire, which is generally sooner than you planned.