By forming an interest group with other shareholders, so that you have enough votes to determine what happens with the companies assets (in an extreme case).

You also have some legal rights as a shareholder. I don't know about the US, but for example in my country there is a LEGAL requirement for companies to maximize shareholder value. Few people seem to know when they blame capitalist greed, when really it is a government law. So you can sue the company if you think they mismanage their assets.

Of course there are ways for companies to rip off shareholders. I think there is an old Philip Greenspun article about it, iirc he mentions buying expensive furniture and artwork for the offices.

I suppose it is part of the due dilligence before investing in a company, to check how they spend their money.