This was originally supposed to be a three part episode. The battle at Wolf 359 was originally going to be shown in episode as well. Additionally, both Picard and Data were supposed to be assimilated by the Borg and be combined as one unit. Budgetary concerns forced producers to edit the story down to a two part episode.
Prior to filming, LeVar Burton had surgery and his scenes were carefully filmed after the majority of production was concluded; this is why he only appears in close-ups and not in shots with any of the other main characters. Most of Geordi LaForge's lines were given to Colm Meaney's Mr. O'Brien.
The 39 ships comprised both Federation and Klingon ships, however, no Klingon ships were seen in the wreckage. Perhaps due to their habit of going on a collision course with enemy ships as a last resort, the remains of Klingon ships are not among the other ships.
This two-part episode contained 'graveyard' scenes full of wrecked and/or abandoned star-ships. These scenes were populated with study models that were considered for use in Star Trek: The Motion Picture (1979) (as possible versions of the Enterprise) and Star Trek III: The Search for Spock (1984) (as the Excelsior). Some of the other wrecked ships were created via "kit-bashing," or by quickly mixing starship parts from many different models.
Spoofed in the early to mid 1990's via email (and possibly websites). The Enterprise uploaded Windows to defeat the Borg ship. It can be found online by Googling "microsoft defeats the Borg" or "Microsoft vs. the Borg".
The trivia items below may give away important plot points.
The Locutus story line was influenced by the uncertainty of whether Patrick Stewart would renew his contract for another season. Stewart could have decided to leave the show at this point, in which case Jean-Luc Picard would have been killed off in this chapter, and the series would have continued with William Riker as the Captain.
It is explained in Star Trek: Deep Space Nine: Emissary (1993) that the USS Saratoga which is destroyed by the Borg During The Battle of Wolf 359, was the Federation ship Benjaiman Sisko served aboard as ship's first officer, which Sisko's wife Jennifer was killed, prior to Sisko being promoted to the rank of commander and assigned to command the newly christened space station Deep Space Nine.
In Star Trek: First Contact (1996), Picard states that the Borg abducted him and turned him into Locutus of Borg, 6 years earlier. Star Trek: The Next Generation: The Best of Both World: Part 2 (1990) was broadcast 6 years before the film's release.