The secret is to make sure the reader knows which POV you are using at the time. One common way to do this is to simply write which POV is being used at the beginning of a chapter, as a chapter title, and then make sure that POV is used through that whole chapter.

You can switch in the middle of chapters — or vary POVs by paragraphs — but that’s a little more complicated for the reader so make sure he/she knows who’s doing and saying what.

When you are done writing, go back and read what you wrote. If you don’t know who is who, then your reader definitely won’t. Or, better yet, have an honest friend read it and see what they say. Just make sure you are asking them ONLY to determine if it’s easy to know which POV you are using so you won’t end up with a complete critique of your work that wasn’t what you wanted!