What do you use to determine if the market or a security is overpriced?

Caveat: this post is only to compare due diligence methods – this is not a “timing the market” post or “timing the bottom” post.

There are a lot of metrics and I am interested in learning people's theories on what they use to determine valuation regardless of if the market is bull, bear, or sideways. I am hoping to learn why people use the methods that they use.

When determining if the market is overpriced, do you tend to look at this through the lens of an index, a sector or industry, or individual company?

And irrespective of that, what metrics do you prefer to use when determining valuation?

Do you compare current prices to the 52W Low? Do you use PEG ratio? Price to sales? Price to book?

Do you use moving averages? Do you incorporate Morningstar ratings?

Ultimately, I'd like to learn what your preferred methods are for determining that the market or a particular company's current price is inflated and why you use the ones that you use.