Autumn brings, among other things, a return to school activities, some of them involving parades and processions, many of which parents want to record. It doesn't always work out: Taking sharp photos of moving people takes practice and preplanning. It's impossible to stay sharp on a subject moving toward you or away from you, but there are several ways to lick this problem.
The easiest is to choose a camera position at about a 45-degree angle to the oncoming action and pre-focus on an object or a subject that the marcher will have to pass. The object can be a crack in the pavement (cobblestoned streets are easy), a light pole or parking meter or even an overhead traffic light. Subjects to focus on can be bystanders, a traffic cop or marchers when they slow down or stop to rest.
You don't have to be right on the money in this kind of focusing because from a 45-degree angle you have an arc of focus. Practice some dry shots on the bystanders before the parade arrives to see how near and far you are in focus at the f/stop you're using.
Sharpness of focus (depth of field) is affected by both the f/stop and the focal length of your lens. Because of this, the shorter the focal length -- such as a wide-angle 28-mm -- the sharper your picture will be; and the more you stop down, that is from say f/4 to f/8, the more depth of sharpness will result.
You can use these twin factors of using a wide-angle lens and stopping down to help cut your margin of focus error. And if you're insecure, just check the depth-of-field markings on the lens and be reassured that the more you stop down the sharper you'll be.
If you choose the wide-angle solution, just changing your lens will give you increased sharpness at the same f/stop, so means that you don't have to change the shutter speed. But if you choose to simply stop down to a smaller opening, you'll have to slow down the shutter to compensate, and the only way you can still shoot at the original shutter setting is to change to a faster film.
The way this works in practice is to first set your shutter speed at 1/125th of a second and stop down to adjust for the light. If the setting with your normal lens is, say, f/2.8 or f/4, then consider changing to a wide-angle -- or if you don't have one, to a faster film. (For example, changing from Kodachrome 25, with a setting of 1/125th at f/2.8 on a dull day, to High Speed Ektachrome 400, which would enable you to shoot at 1/125th at f/11.)
If you are a tele-fan, your focusing will have to be tighter. Even with a moderate telephoto lens in the 100-mm-plus class, your depth of field will fall off -- fast. The only remedy for this is to be sure to shoot when the subject steps right on your spot, not before or after. You can better the odds by taking a position that lets you pan with the movement, so you can swing your camera with the subject at near right angles and keep it sharp because it's not moving near or far but across your field of focus.
Your viewpoint will have just as great an influence on the success of your parade pictures.
Try to get to the scene early so that you can pick an unobstructed viewpoint. The best is where the marchers make a turn or by the reviewing stand when they're all alert. If you can't get a clear shot because the crowds are already there, look for an overhead vantage point. Sometimes you can persuade others to share a window, or there may be some steps from which you can shoot over the heads of the bystanders. I've even carried a small aluminum ladder and shot over the heads without butting in.