A putting mirror, rulers or chalk line are tools to help with proper putter face alignment off the course. But on the course is a different story. One tool that is very popular is the line on the ball. I like to use it on slippery left to right putts since I tend to line up to the right.
Another tool is spot putting. It is much easier to find a spot a few feet away and line up than 15 foot away near the hole. Also experiment with alignment aids on your putter like circles, lines or none at all.
But if you want to get on a roll, don’t worry too much about alignment and stroke….focus on speed and your target longer than the ball.