Speaking of old guys, from Chgowiz we have this bit of wisdom:
The freedom I have with the sandbox is also an exercise in "What If" for me. I've got a running series of events that progess as time goes on. The players make choices that might involve them, or they may ignore those things, but if an army is going to invade, then it'll invade unless the players choose to get involved. The nice thing is that they don't have to - this is their game. I'm going to react accordingly.
This does force me to be more reactive in some of the outcomes. That's both a curse and a blessing. I have to run by the seat of my pants, within a broad set of objectives. If the players had ignored the goblin's request, then I would have had to come up, in game, to what would happen. It's nice, though, because I don't have to plot out and railroad outcomes far in advance - I can allow the world to evolve and react accordingly to the scope of events that the players involve themselves in. In this case, I had no idea how things would go, but I knew my NPCs and I knew the setup.
In both cases, we see “rulings, not rules” in action. The neo-classical GM, attempting to meld a living campaign with the sandbox principles that allow players nearly unlimited choice, simply can't have everything planned out in advance, whether its the events of a battle or ebb and flow of a campaign-spanning story arc. Playing fast, loose, and flexible is the rule of the day.
Luckily, this gets easier as you go along. The simplicity of most old-school rules systems make it very easy to give players one-time bonuses for good ideas, and invite the players to interact with their environment, whether at the physical or political level, without fear that they have the wrong feats or skills. It does require a certain amount of courage on everyone's part. The players have to trust the GM to be fair, but also understand that “fair” cuts both ways, be willing to live with the consequences when things don't roll their way. The GM has to be willing to get it wrong sometimes, and be brave enough to admit that and fix it when it happens. It requires that everybody be open and honest about their desires for the game and what is required for their idea of fun.
The results, however, are a game in which the boundaries are broad, but a core of solid predictability holds it all together. It gives what I consider to be the optimal combination of rigid framework and playful flexibility.
Photo credits: charliejb and wili_hybrid.