Long ago, the noun lede was an alternative spelling of lead, but now lede is newspaper jargon for the introductory portion of a news story. Lede is confined to very narrow contexts. Unless you’re referring specifically to the first sentence of a news story, go with lead. (Lede also occasionally denotes the leading story in a newspaper or magazine, but this too is newspaper jargon, and most of us will never have need of it.)
Lede also appears, sometimes figuratively, in the expression bury the lede, meaning to begin a news story with nonessential details. Bury the lead sort of works, but bury the lede is the conventional spelling of this expression.
Examples
These writers illustrate where lede is appropriate:
The lede of Anne Marshall’s cover story in today’s City Paper grabs you by the collar … [Nashville Scene]
Most games weren’t even close, and let me tell you, coming up with a snappy lede for a 50-point blowout was beyond difficult. [mlive.com]
The Weiner quote was the lede in a notably vicious profile of Sadik-Khan in The New York Times … [Crosscut]
And in the following example, lede is used outside its narrow definition, so it would bear replacement with lead:
And it’s rather odd that the lede Gallup chose to pursue in reporting these results was that Obama had majority approval in environmental issues … [Hot Air]
This sentence uses lede to mean something that guides or directs, which is squarely in the purview of lead.

