One of the things I think most obviously separates pulp fantasy from high fantasy is its literary format. While there are many pulp fantasy novels, the short story (and its cousins, the novelette and the novella) is the genre's true home and it's generally a good bet that a fantasy tale written as a short story is more likely to be a pulp fantasy than a high fantasy. It's no accident in my opinion that many of the strongest influences on early Dungeons & Dragons were short stories. Indeed, I would argue that D&D works best when a campaign consists of episodic "short stories" rather than a lengthy epic "novel."
Unfortunately, the short story seems to have fallen into disfavor, particularly in the fantasy genre, where multi-book series seem to be the norm. It's refreshing to remember that this wasn't always the case and one needn't return to the 1940s or 50s to find terrific examples of episodic fantasy. 1979, for example, saw the publication of Thieves' World, the first of twelve shared world anthologies edited by Robert Asprin concerning the inhabitants of the dissolute city of Sanctuary.
Several things elevated the Thieves' World series in my estimation, chief among them being the diversity of its authors. The first volume included short stories by Asprin, Lynn Abbey, Poul Anderson, Joe Haldeman, Andrew Offutt, and Marion Zimmer Bradley, among others. Later installments in the series included authors such as Philip José Farmer, David Drake, A.E. van Vogt, and C.J. Cherryh. As a result, the stories, especially the early ones, never fall into a rut or become repetitive, as each author brought a different perspective and style with their contributions. The series was also notable for its excellent setting and characters. Sanctuary is a wretched hive of scum and villainy that is no mere pastiche of Lankhmar, even if it clearly pays homage to Leiber's creation. Similarly, the characters of Thieves' World -- Lythal the Star-Browed, Jubal, One Thumb, and others -- are worthy to join the pantheon of great pulp fantasy protagonists ("heroes" is too unambiguous a word to describe them).
The Thieves' World series lasted for a decade, the last volume in the original series being published in 1989. As the series wore on, it showed signs of tiredness. There were fewer and fewer different contributors to each volume, with most of the short stories written by a handful of authors. Likewise, the episodic, picaresque nature of the series became less strong, as several overarching stories came to the fore, some of which veered a bit too much toward high fantasy for my liking. Even so, it's hard not to be impressed by the original volume and its immediate sequels. They injected some much-needed vibrancy into the pulp fantasy genre and their tales of Sanctuary's burglars and bandits, rebels and rapscallions remain among my favorite "modern" fantasy stories.