Adventure games have a long history, one marked by many great works, though tempered by some flaws. Today, their relevance in gaming has declined, but a few games and remakes are still adopting the genre. We tropers should not let the genre die; we should encourage its renewal.
Writing is an essential aspect of the genre, as these games use little action. Most of the great adventure games had detailed, well-written descriptions for every object, and a wide variety of unnecessary action. Your motto should combine Developers' Foresight, and Have a Nice Death. Gamers will search for every possible option, and they should be rewarded for their curiosity with humorous results, including numerous amusing deaths.
Half of the fun in an adventure game derives from finding all the ways to die. Sierra—in its glory days—and Infocom, two of the defining adventure game companies, filled their games with amusing deaths. One of the best moments in the Space Quest series was when the player could stick his face, or arm into a pit of acid, with the logical results. LucasArts is the exception that proves you don't really need to kill off your players every five seconds. Dying, however, is not the same as making the game unwinnable.
Unwinnable, though a common trope in this type of game, is to be avoided, or at the very least treated with extreme restraint. Players hate the frustration of finding that they are trapped because of some minor mistake made hours earlier, and though many of the best games have such scenarios, that does not make the trope any less frustrating. Careful puzzle design avoids such problems. Generally, one should try to avoid going futher down than "Polite" on the scale listed on Unwinnable by Design.
Resist the temptation to indulge in overly sadistic design and Trial-and-Error Gameplay. Consider that maybe it might be more fun for players to figure out the game for themselves instead of figuring it out by making millions of mistakes. Too Many Deaths of You can wreck your Willing Suspension of Disbelief. As David Fox said, unlike in Sierra games, in the real world you can successfully pick up a broken piece of mirror without dying.
Item-manipulation puzzles, which were standard before the days of Full Motion Video, are best: Myst-style mechanical puzzles tend to be tedious, and repetitive, and the older games that rarely used them tended to be much better than later games. An occasional Moon Logic Puzzle is acceptable, as adventure gamers think laterally, and enjoy exploring every possible option. Unsuccessful attempts to solve puzzles should be met with amusing responses, and deaths. As of circa Grim Fandango, adventure games had a propensity for the player to almost solve the puzzle, demonstrating that something further needed to be done. This shows the player that they're thinking along the right lines and adds at least one additional puzzle inside of the puzzle. A straight-forward example of this from Grim Fandango is that the player is shown that they have to slow the airflow in a tube messaging system. They can insert a playing card, but that stops the airflow completely and the card is blown through the tubes when the pressure builds up. The solution is to then punch holes in the card to slow the air flow down enough without pressure building up.
King's Quest VI, Leisure Suit Larry 1, 2, 3, 6, Space Quest 1, 3, 4, 5, Police Quest 1, 2, 3, Perdition's Flames, Gabriel Knight: Sins of the Fathers, Zork, Maniac Mansion, Zak McKracken and the Alien Mindbenders, Indiana Jones and the Fate of Atlantis, Loom, The Secret of Monkey Island, Monkey Island 2: LeChuck's Revenge, The Curse of Monkey Island, Day of the Tentacle, Sam & Max Hit the Road, Full Throttle, The Dig, Grim Fandango, I Have No Mouth and I Must Scream, The Legend of Kyrandia.