How do I remove paint from a pallet?

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I bought my 10 year old son a real wooden art easel for Christmas. I don't know anything about painting and am not very artistic myself, except for writing. My son is very creative and can draw very well. I want him to increase his artistic abilities. He has some acrylic, oil, and watercolor paint. How do I remove the paint from the pallet after using it? What works with getting paint out of clothes?