Cliffy B. was one of the level designers on Unreal and Unreal Tournament. I got these tips from his website years ago and kept it in a document on my desktop, this here would be a better place for this good info.
Controlled Freedom
Let the player think he has a choice in where to go and what to do but gently guide him to his
destination.
This is an avidly debated topic; if a player has the freedom to go anywhere and do anything (as
many gamers claim they want) then he will quickly get lost and frustrated. By keeping level design
somewhat linear and giving the illusion that there are multiple paths one has the freedom to
choose then the player will have a more enjoyable play experience. This way, the player
experiences the best of both worlds; the player gets to the carrot on the end of the stick, and feels
like he made the right decisions on where to go.
This can take more time to design but ultimately adds up for a more enjoyable single player
experience for the user. It is completely possible to build a title that revolves around the notion of
"go anywhere, do anything" but a developer who does this must allocate plenty of time and funding
to make this a reality. Often previous titles that have had very much "open-ended" designs have
had users that have found themselves lost and asking "what do I do next?" Only the most hardcore
of the hardcore gamer will stick with a title that is too open-ended. It can be done; it simply
requires longer design times and a more focused and dedicated user.
Pacing
Constant scares dull the senses.
The scariest horror movies are the ones that lull the viewers into a false sense of security and then
spring something scary upon them, and a great level is no different. An excellent recent example
of this is System Shock 2. One minute the player is being chased down by pipe wielding maniac
hybrids, the next he's tucked away in a quiet bedroom aboard the Von Braun, reading log files
from dead crewmembers while wondering what will be around the next corner. If the monsters
were constantly in the player's face the game would cease to be scary. However, the down time
lets the player forget, for a moment, the peril that he is in? just long enough so that his guard
drops and he's scared (and killed) by the next baddie.
Risk Incentive
In single player design, there are oodles of ways a designer can utilize this time tested technique
to let the gamer make his own decisions about how much trouble he's going to get himself into for
treasure.
That's the beauty of risk incentive. The player weighs the risk; he assesses the challenge, and
gets to make a decision. He feels like he's in control, and the designer provides him with a
choice.
For example, in a traditional shooter the designer might place ammunition or health below a pair
of sentry turrets. The turrets can easily be avoided by crawling behind a pair of desks, however if
the player wants to make a dash for the goodies it is his choice. Therefore, if the guns rip him to
shreds and he screws up he blames himself, not the designers.
On Revisiting
The concept of "Revisiting" or "Doubling Back" refers to the gamer seeing an inaccessible area
of a level and wondering "How do I get there?" The gamer then proceeds to complete a series of
tasks which move the game/story along (as well as his virtual self) and he then suddenly looks
around and realizes "Oh! I'm up there now!"
Revisiting areas from a different angle is a good thing for designers to practice. It keeps the
gamer motivated as he tears through your designs, as well as saving time and money. The same
rooms are viewed from multiple angles as well as revisited, and this saves the designer from
building more areas. This will be more and more of a blessing as levels become more detailed
and expensive to produce in the near future.
Supply And Demand
Leave the gamer always concerned about running out of ammunition and/or health, but not to the
point where he's running around bullet-less, dying constantly, while cursing the designers and their
product. This is yet another carrot on the end of the stick trick that makes for a satisfying gaming
run. It teaches resource management, and makes it a better experience when the gamer finds
health and ammo. Good supply and demand makes these goodies more valuable.
Scene Composition and Contrast
Relatively simple objects arranged in an interesting method can result in a far more eye-pleasing
image. This is true with art, architecture and, of course, level design. It becomes especially
relevant when working with low-polygon geometry and strict detail budgets.
Many art classes will spend time focusing on the idea of scene composition. This is another
example where an art background will come in handy for a designer.
Work With The AI Guy
AI is tied directly into the structure and composition of a level. It is where the AI does its thing, it is
the place where all that hard work on the part of the AI guy is supposed to be shown.
It is crucial for a level designer to construct areas that take advantage of the AI while working with
the AI guy and figuring out what the AI is going to do. For instance, if there is an AI that is really
good in firefights, ducking behind boxes and taking pot shots at the player, a designer should plan
to build an environment with waist high crates all over the place. If the AI guru programs a great
pack AI, make space that accommodates it. Often AI does not work perfectly, it is important to
maintain patience and have faith in the AI talent as the designers manage to iron out kinks in the
system.
Smart designers and programmers will work together to create memorable scenes where puzzles
and areas are built around crafty artificial intelligence.
On Sound
Steven King, in Danse Macabre, said something along the lines of:
"When the lightning crashes and the door opens and you see a ten foot bug standing there, a part
of you sighs and thinks "Whew, I thought it was going to be a TWENTY foot bug."
Designers must work closely with sound technicians to assure a compelling and exciting audio
experience. A great designer never underestimates how much mileage he can get out of a good
bump in the night. No matter how good the talent is, the monster that is in the gamer's head is
always scarier than what is seen onscreen. If the title calls for chills and thrills, let the sound do
much of the work!
Intelligent Backtracking
If a designer is forcing a gamer to backtrack he must make sure that it is done in a logical and
non-frustrating manner. This is a dangerous time in design, as the "carrot on the stick" of seeing a
new area is gone. A designer is re-using a previously seen area and it is important to make the
area seem fresh or interesting as the player navigates it. This often requires subtle scene
changes, or the addition of new hostiles to prevent the area from seeming "dead" and "used."
Much like a used-car dealer will polish up an older model, a designer who is re-using an area
must put more effort into it to make sure that it seems new and fresh.
It is also key to make sure that the gamer does not get lost as he is backtracking. If, for example, a
gamer must activate a pump so he may drain an area with waste and cross then the route back to
the previously hazardous area had better be pretty easy to navigate in reverse. Using controlled
freedom here will ensure that the gamer knows where he's going; perhaps by blocking off a
redundant area or placing highly visible signs that direct him on where to go he'll have more fun.