Depends...I have a by-pass humidifier in my system, and to switch over I (should) close the bypass duct damper.
On some systems, you might get better operation if you switch the fan speed, but that isn't as common.
You should change the filter more often than change of seasons! but other than that, flipping the switch may be adequate.
Some houses are installed with multiple exhaust registers...it works better to exhaust cooled air high and heated air low. If you have multiple ducts, both high and low, close the lower ones and open the higher ones.
My house is an open design and I find in the winter I direct much of the heat downstairs and it gets upstairs. In the summer, I direct most of the cooling upstairs, and it gets downstairs. Having good return ducts may change your operating parameters.