A hand saw comes into contact with a piece of wood and the result is usually a wobbly cut. The saw drifts, the teeth chatter, and what was a straight pencil mark is transformed into a kinked one in the first couple of seconds. You can’t force a saw to be straight by applying raw power. Instead, you need to focus on proper orientation and motion. Start by drawing a short line on a piece of practice wood and stand so that your eye is directly over the line (not looking at it from an angle). Then move the saw so it feels like it is riding in a track along the line. The motion should come mostly from your shoulder, not your wrist. If you understand this from the outset, you are less likely to rotate the handle in the middle of a stroke, which is where the drifting usually begins.
Don’t worry so much about your grip. I know it seems like a death grip would be better, but you would be surprised at how rigid this makes your arm. It’s easier to make a bad cut when you squeeze the handle too hard. Squeeze hard enough to control the saw, but not so hard that you prevent the teeth from biting. Begin with just a couple of light back-and-forth strokes to get the cut started. Use your body weight to keep the blade’s teeth in contact with the wood, but don’t bear down on the blade. This is where many new saw users go wrong. They push down too soon and too hard. The teeth bite into the wood inconsistently and the blade is pulled away from your intended cutline.
Even fifteen minutes can be a valuable practice session. On a spare board, draw five lines that are a couple of centimeters apart and saw them one by one slowly. Your goal isn’t to do this as quickly as possible, but as steadily as you can. After each cut, look at the side of the board and then at the other side. If the kerf is not perfectly vertical, then your blade was not perfectly vertical while you were cutting. This time don’t adjust your hands, but your feet. Arrange your feet in such a way that the cutting action feels natural. Every time you reflect on your actions, you are practicing.
Another common error is looking at the teeth at the front of the blade, rather than the line. This fosters micro adjustments that result in a wavy line. Look instead where the blade enters the wood at the end of the stroke. Your body will automatically track to that point. If the line begins to wander, don’t force the blade back onto the line, reduce the pressure and allow the saw to slowly find its way back. Forcing it is almost guaranteed to increase the kerf and decrease accuracy.
After a while, the clean cuts start to seem quiet and silky, even easy. The noise goes from a loud rasping to a steady hiss, which tells you that the teeth are cutting, not ripping. Doing this tiny practice a few times in a row accomplishes all of this in a hurry compared to trying a full-on project right out of the gate. If you can cut a line straight on scrap wood, then joints and straight edge trimming become much less daunting, since the basic action is already second-nature.