Lately I've challenged myself to conjure up game mechanics that test my players' abilities to improvise and innovate within a particular game setting. Most of my recent game ideas have sprung from the concept of a prehistory fantasy setting, and this conjecture is no different.
I'm curious, to say the least, about what players would do in a setting that asks them to move forward in a four-dimensional campaign, rather than through the traditional three. What if players not only have to solve local temporal issues of 'find this' or 'kill this' or 'save this', but are actually responsible for a culture's progression, technologically-speaking? What if-and this is where my brain starts actually overheating-players were the ones who decided how gods and magic appeared in the world?
What does this mean for players?
Well, obviously it represents a drastic shift in the objectives of the players themselves. They can't be passive receptacles for plot; at least not all the time. Players have to look at their game world not as something static, but as an evolving machine that they do not have all the schematics for.
Obviously there must be strictures in place, because despite our best intentions, there's going to be a type of player that 'decides' he's going to discover that magic comes from his farts. It's important to have the requirements of your world in place, what you might call the world's natural laws. Perhaps the manifestation of magic requires a substantial sacrifice by the user. Perhaps it requires an appeal to a god, who may or may not even exist yet. Having these canonical and physical restrictions in place draw the line between the campaign where players refill their mana by eating beans (god help you, poor GM) and the campaign where one mostly-annoying PC spends a few days in a cave farting and (hopefully) realizes that maybe something else needs to happen first, or in addition to his own flatulence.
There is also the concept of need-based innovation. Fire was invented (or brought down from on high by Prometheus, depending on your worldview) because humanity needed something to keep the chill of night away, or to keep the monsters at bay. Wheels came about due to the need to transport quantities of goods that a normal human couldn't carry effectively on their own. But what if your players don't ever encounter that problem? What if they could bribe a giant into doing all their heavy lifting? The need for innovation drastically decreases when that first 'want' is already alleviated by a historically unorthodox solution (in terms of the real world).
What does this mean for GMs?
As already stated, you need a set of guidelines as to how players will interact with and develop technology; however, this is only for your purposes. The last thing you should be giving players is any kind of handout detailing exactly what, step for step, they need to do to accomplish what they set out to do.
Instead, what you should do is ask your players what their goals are: short term, mid term, and long term. Obviously you should have some quest lines for them to follow while you're plotting out how to incorporate what they want to do in the story BUT - and this is an important but - after finding out what your players want to do, start incorporating some of the how into that generic session. So, for instance, if a player wants to invent or discover wizardry, bring in an NPC character that is old and wizened. Have them be a master in some kind of wizardry (preferably not all wizardry), but also express in their description and dialogue exactly how long it's taken them to master this tiny aspect of the arcane.
Thus, without providing your players with some kind of generic checklist, they get an inkling of the concept of sacrifice and determination that is required to achieve their goals. It gives intuitive players an idea of where to start with their objectives, but allows them to connect the dots without handholding, so they can take the concept of what you've presented and maybe put their own unique spin on it.
Now, obviously, this puts quite a bit of work on the GM in the front-end. You'll be crafting concepts and natural laws in addition to NPCs, quests, conflicts, etc. However, once players get the hang of the concept you're trying to impart onto them, it's likely they'll use the laws you have in place and come up with their own solutions.
Just some food for thought.