Buy one or two mineral books. The internet is a good source, too. For instance, you find a green rock. You note it looks like a crystal of some sort. Type green minerals into your browser, click on that and then when you choose a rock that is similar to yours, type its name in. If they just show you gems, type in rough jade or rough emerald. Then tap images. They will show you pictures in rough, natural, uncut condition. The pictures will now show you something closer to the rock youhave. In many cases you will successfully identify your sample. That will go a long way towards deciding how to clean it. Heat, light, exposure to air or dofferent chemicals can be dangerous.
Example: small piece of sodium metal, if you try to wash it in water, BOOM,!!!
Small piece of plutonium, you might die.
In other words, handle samples carefully, identify them if you can and be careful. If I have a question,I take it to the rock store nearest my home, or a rock show.
There are too many different compounds and minerals to list them all. Once you identify it, you can ask us or any internet source or rock shop, then we can advise you. Some rocks are so unstable or fragile, any handlig at all will ruin them. But most are just rocks. Pictures will help us help you. Warm water and a toothbrush will remove most surface dirt from your samples