There are plenty of zombies and evil creatures after you in Resident Evil 3: Remake. Due to this horde's massive hunger for your flesh, it may seem like the odds are always stacked against you. Of course, you have a lot of guns against them, but you don't have a lot of ammo. A great way to conserve ammo is to perform Perfect Dodge. However, perfect dodging takes a bit of practice.
Perfect dodge with Jill
Jill is the one doing the perfect dodge, so we'll focus on her technique first.
You must wait for the zombie to get close enough to you to attempt an attack. Prepare by pressing the RB / R1 button, then pushing the left stick in a direction away from the enemy as they begin to attack. Shortly after, turn to face the enemy and shoot them, hopefully with a headshot at the right time to deal heavy damage.
When you do the perfect dodge correctly, the game should bring your reticle immediately to the enemy's head, giving you the best shot to do the most damage. Time also slows down for your convenience. You'll know you've rolled and dodged in the correct window because there is a distinct sound that goes off when it occurs. If you hear that sound, you'll know you've done it right, and you can start doing it more often by following the technique.
Perfect parade with Carlos
When you play as Carlos, he functions almost entirely the same, except he does a counter punch instead of a dodge. It works a little differently but follows the same button pattern.
When an enemy is about to grab you, press the RB / R1 button and hit them pushing them back. You want to move your controller away from the enemy at the same time. The attack should knock the enemy onto their backs, giving you a free kick with their head for a few seconds. You can do this multiple times against enemies, one after the other.
You want to practice both of these skills quite often, so try saving the game and chasing a few zombies at the start of your game to test it out. Once you get the hang of it, reload your save and fight them again, honing your technique.