Learning to use a whetstone is the best thing you can do for your knives, especially nice ones, but learning how can be tricky. Luckily, this (very detailed) guide from KnifePlanet teaches you how, from start to finish, and includes a simple method for making sure you've sharpened enough to make a difference.
The "Sharpie Trick", as they call it, is simple:
Speaking of building muscle memory, here is a good exercise for you, a confidence builder: Paint the edge of your knife and bevel with a Sharpie and sharpen the knife at an angle that results in the removal of that Sharpie. In many cases it will be close to the 20 deg angle anyway. When you have achieved success, repeat the process and do that ten times. Now flip the blade over and do it on the other side, you don't need to use much pressure here, just a little. You want to get to the point where you can place the knife at the SRA "Sharpie Removal Angle" the first time, every time.
You might want to practice getting the angle right on a knife that you're a little less concerned with before you break out your favourite knife and go to work here. We should also mention that the Sharpie trick is actually deep into this guide — if you're starting from the basics and have never used a whetstone, you should start at the beginning, where the guide explains the various grits of stone available, which ones you should choose, and the supplies you'll need for your sharpening station. Luckily, you won't need much — just a whetstone, a stone holder, water, and a towel, not to mention your knife.
From there, it's all about learning the right angles and how to move your knife across the whetstone, how to keep it well lubricated while you do so, and how to feel the changes you make in the burr of the knife as you straighten out the tip. Once you've honed the knife and raised the burr, then you move on to actually refining the blade and making it sharper overall.
The video above is a walkthrough from start to finish, and worth a watch, but if you want to follow step by step, hit the link below. It's definitely worth a bookmark if you want to learn how to do this yourself (as opposed to sending your knives to a pro to be sharpened — who's already mastered this technique.)