This post is built off the article: http://move.themaneater.com/blogs/move-games/2010/4/2/some-fundamental-dos-and-donts-open-world-games/
1.Do: Have a reasonable size open world.
Donít: Make it excessively large.
In general open world games need to have larger and more developed worlds/levels due to the inherent demands of the genre. This allows the player to explore and experience the unrestricted nature of the game. For example, Skyrim is a massive game with plenty of things to do outside of the main storyline, such as exploring dungeons and crafting. However, massive voids are no fun either, a game is about interacting and doing, the open world games shouldnít have areas devoid of content or activity besides walking to another area. In WarZ, the player spent his time moving between locations, doing little more than walking. There is no hard rule to measure this, but if a player can go about a few minutes without any interesting things to do; you probably either need to add something or shrink that area. A few ways to add content to an area without side quests or elaborate areas are by adding collectables, Easter eggs and quick missions (e.g. Rampages in Grand theft Auto).
(The Green and red Point represents indicate the loot drops, while houses show general stores, while other points of interest, such as player/monster spawn and player safe areas arenít shown. Notice the amount of travel/ empty space there is. Game: WARZ)
2.Do: Have a good travel system.
Donít: Waste playerís time by forcing them to re-walk everywhere.
Open world games are not life simulators were the player needs to experience every step of an activity. While side activities, such as smithing, are usually pace well, travel has sometimes been an issue in this genre. Two particularly excellent travel systems are the abundant transport method (such as GTA series), and the limited fast travel systems (such as Pokťmon and Bethesda RPGS).
In the abundant travel method, the player usually canít teleport to other areas of the world, but has an unlimited access to fast transport. In the GTA games cars are literally all around and if you destroy your vehicle another one is waiting to be taken. Unlike Skyrim, where getting a horse is a process and on the spot replacement is nearly impossible.
The fast travels system allows you to teleport to previously visited location or set areas. In Skyrim this is the primary way of getting around. The player usually fast travels to the closest previously visited locations and make their journey to new locations from there. In Pokťmon, (I only played up to pre-leaf green and fire red generation) fast travel is limited in the beginning and more available once fly is gained. This is offset by the localized nature of the challenges and limited fast travel items and abilities such as escape rope and dig.
( A game all about travel that was meaning full and engaging. Game: Journey)
3.Do: Have side missions with a random element:
Donít: Have cookie cutter areas/ extras
With the size and scope of open world games there will be a need to reuse existing content to fill space. By adding variable elements, a developer can change pacing or flow, for instance, let's say a particular dungeon is reused a few times, but instead of offering the same enemies puzzles or loot, have these elements vary randomly with each encounter. This will also add variety, if the player chooses to replays the game from scratch. So once the player enters a dungeon, make the game then generate variable elements randomly, such as which npc type to spawn, how to preset puzzles and what loot to offer. This will allow a player enter similar areas, while changing the method used to accomplished the same area and what benefits the player gets from completing an area. This works well in a story independent area, and were a certainty outcome isn't expected. In the borderlands game, most weapons are randomly generated, thus you can open the same loot container and get radically different results each time.
(Try to find 2 items the same. Game: Borderlands Series)
4.Do: Make a reason to explore.
Donít: Front load the game.
Exploration is probably done best in open world games. This is due to the raw size of these games and large variety of rewards. However, I have seen in some open world games the exploring aspect of the game killed in one of three ways. First, by not providing enough variety or lack of a reward, second it's too difficult and third by front loading a game with especially strong beginning items. Games are very result driven, and gamers play to accomplish objectives, thus the effect required to accomplish a task is proportional to the expected reward or outcome, such as when players grind in order to power level. Exploring a large world is time consuming and players expect that the exploration will lead to somewhere or something. If the journey or reward is sub-par then players will be less likely to explore in the future.
If the game is over hard, players will be less likely to explore either due to frustration or the cost to benefit ratio, mentioned above, is not in their favor. Most modern games are not marketed on how hard they are and in some cases just the opposite. With the rise of social (Facebook)/ casual market, ease of play is preferred. Usually gaming adults have more responsibilities and less time to game then younger audiences. So we don't have the time to play extremely hard games that requires a time consuming raw trial and error approach. Plus, games are no longer burden by early limitations that forced them to be harder in order to pad out game length. Also, some players prefer, story over challenge and may be turned off by extremely hard games. (Not all fit players in this category, but I feel this is a safe generalization to make).
Lastly, we have the problem where the starting items are more powerful than items gained earlier in the game. This problem usually appears with pre-order dlc where the player is given a pre-order bonus in the form of special starting items that are better than the normal ones. Now if done correctly, this will allow the player to experience the game beginning at a quicker pace and get into the meat of the game faster. However, when done incorrectly this will accelerate the beginning faster than intended, leading to shorter game length or causes a stall when the player's special items are inadequate for further progression, forcing the player to backtrack to look for proper items.
5.Do: Have sandbox elements
Donít: Make these elements redundant or repetitive
An open world game should allow its player to be a part of itís world and interactive in a meaningful way. This is we're the edition of sandbox elements come in nicely. In Skyrim, even when not doing a mission there is still something to do, such as mining, smithing, and potion crafting. Also, there are real consequences to you actions, if you steal or murder in town the guards will attack, fine or imprison you. When compared to the Mass Effect series, the differences are noticeable. The most striking example is how non-combat npcís behave, they are props that stand in one place or walk in ridiculously linear paths, with little or no interactive AI. Second, is the limited number, of activities in non combat times. On the Citadel, there are only a few things to do such as questing (fetch quests) or shopping.
When implementing these elements it is important to do so in a way that doesn't feel repetitive. This can be done by limiting the number of steps needed to complete a task. For instance, smelting in Skyrim is limited to the notable task; notice that the smelting process is an animation loop. Also, it is important to limit the number of repeated actions. Let's say, I want to make 20 iron daggers, the game at smithing time should allow me to make as many as I want at once provided I have enough supplies. There can be a small experience penalty per dagger made in this fashion, to discourage level grinding exploitation. This allows the game to strike a balance where the player can move between tasks faster, but not allow easy level grinding, that breaks pacing.
(Wax Museum, This is what walking through noncombat area of Mass effect was like)