Practice doesn't make perfect. Perfect practice makes perfect. Other articles may tell you the basics of how to putt, but these drills and methods will take you to the next level.
Make your swing the same length as your takeaway. This will encourage better control of distance on your putts. Also, putt with your shoulders and not your arms because using bigger muscles increases your stability and control. You should already have know that though.
Step2
Practice 3 foot putts. These are far from being givens. many people don't even practice 3 foot putts because they assume they'll sink them when they need to. Not the case. You might look silly, but your game will be better than your partner whose practice one handed 40 foot putts. This is also about getting into the mindset that you're going to finish each hole out no matter how close the putts are, and improves your stroke as well.
Step3
Practice lagging to within 3 feet. Set up a long distance from the hole and practice lagging your putt to within 3 feet and not at the hole. Your mind plays games on you when you're going for the hole from so far away. if you can consistently get within 3 feet, you'll eliminate your 3 putts.
Step4
Play more break and aim for behind the hole. If you look at pros, when they miss they miss above and beyond the hole. If the ball never goes past the hole it'll never have a chance of reaching the hole at all. And playing more break than too little break also makes the ball at least go past the hole and give you a chance of sinking the putt.
Step5
Vary your puts. Not every putt is going to be a 4 inch break, 5 foot putt. Practice from every angle, practice every break, and practice every distance.
Step6
On uphill putts, practice compensating for less break and add more speed and for downhill putts, play more break and let gravity do the work.
Step7
Don't be satisfied until you're sinking your putts dead center. That's when you know you're doing things right.