Do you mean suede boots?
The best thing to do is to start with a suede brush and scrub gently any dry dirt or old salt. You can spot clean with a damp cloth. But follow up with a good waterproof spray when you’re done. It’s always good to stuff them with either a newspaper or a shoe form to keep the shape
I've used the brushes they make for suede, but find it easier to use a microfiber cloth.