How to condition supply voltage for project
As a @Hearth says, your PSU should do most of the work. 
You should add some decoupling capacitors around your µController, and you can also (although it's exceedingly unlikely that you'll need it) add a filter (ferrite beads between the psu and the decoupling, or a ferrite with a couple of turns on the +ve and -ve leads bringing in the power). 

If you're worried that your PSU might give you too much voltage and damage your circuit, you can add a crowbar circuit. Like the following:







simulate this circuit &ndash; Schematic created using CircuitLab

This will short out the output of your PSU if the voltage gets too high (people often add a fuse in the input so that the crowbar blows the fuse when it triggers). 

For a simple microcontroller, a Schottky diode on the input, (or a reverse biased diode between +ve and -ve), is usually all you wnat. (to protect you from someone who gets the power the wrong way round)