Amazon (AMZN) has pulled back nearly 10% after hitting an all-time high last week, but dip buyers should remember that RadioShack once seemed like a bargain, too -- until its stock fell to zero, TheStreet's David Yoe Williams says.

"At a certain point when RadioShack was starting to fade, it [looked like] a buy at $15, $10, $5, a dollar-and-a-half -- [except] it wasn't," Williams said during TheStreet's August Trading Strategies roundtable discussion.

"Everybody said Amazon was so great and [is] going to kill [traditional] retail, but come to find out maybe it hasn't," he said. "It's really only 20 percent of the market."

Williams said investors thinking of buying Amazon or other red-hot tech stocks need to remember "basics and fundamentals -- you buy low and you sell high."

"I don't care if you're in bonds. I don't care if you're in the equities. I don't care if you're in gold -- you look for assets that are undervalued and you buy them, and you sell assets that are fully valued or fairly valued," he said. "If [we] are eight years into a bull run and you're telling me: 'I want to buy techs at this spot,' I would say: 'I'd rather go into energies and basic fundamentals.'"

Amazon's shares fell 0.9% to $987.33 by Thursday's close.

You can check out our entire August Trading Strategies roundtable here. Or, read more of our columnists' August advice at:

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