You have an alternate airport on the flight plan. Fine. What would make you go there?
If the answer is “I guess I would figure that out when I got close,” you have named an airport. You have not given yourself much of a plan.
An alternate should be useful when the trip starts to change, while you still have time and fuel to make a calm decision.
Give the option a job
Maybe the destination weather may deteriorate. Maybe a line of storms could cut across your route. Maybe you need a place to land soon after departure if you cannot return. Those are different problems, and one airport does not necessarily solve all of them.
For a weather problem halfway through the trip, I want to know where I could stop before I fly into the worst of it. For an arrival problem, I want to know which airport offers a genuinely different option and whether I can get there with fuel to spare under the conditions I expect. I want to look at the weather, runway, procedures and any airport information that could change the answer.
Then comes the part pilots often skip: the decision point. What would you need to see to continue? What would make you land and wait? What would make you turn toward another airport now instead of ten minutes from now?
Those questions are easier to answer at the kitchen table than while you are in the clouds explaining a reroute to ATC.
Keep checking the plan
Planning an option does not make it permanent. Weather can change at your alternate, too. Fuel use can differ from your expectation. A runway can close. You still need to check whether the plan works when the moment arrives.
That is one reason I think in terms of alternate courses of action, not just an alternate airport. A later departure, a different route or a fuel stop may be more useful than hoping to finish the original trip in one shot.
I once headed toward a family reunion without checking that the destination runway was open. Memphis Center told me about the closure halfway there. We found another airport and landed. It worked out, but the lesson was pretty obvious: an option discovered by luck is a poor substitute for preparation.
Before your next trip, point to each airport you have chosen and finish this sentence: “I would use this one if...” If you cannot, take a few more minutes on the ground and make it a real option.