To be honest, the best GUI elements are complete lack of them on the screen. Minimal is a very good rule of thumb for any GUI. The less elements that are shown on the screen at once, the better the chance that you won’t have a very cluttered and distracting GUI.
In general, you want to make sure your GUI is completely “out of the way”. There are few cases where any element is more important than the game play itself. You want to keep all those other elements away from the middle of the screen and put them more toward the edge of the screen.
Secondly, you have to be very keen to what kind of game you are designing. As a general rule, I realized that most GUI’s follow the convention of using the top to display general information (like timers, health bars, and ailments). The use the bottom bars for more crucial (and interactive) information (like inventory items, power-ups, and menus).
“If your game has a lot of action sequences and you are forced to have to click and inventory over and over again. You might want to assign these sequences to predefined keys or put the inventory near the bottom edge of the screen. Things like the health bars or statistics are usually put near the top of the screen since you won’t be interacting with them often.”
I believe the reasoning behind this is that any disruption of visuals because you are forced to click an option is considered a bad thing. Moving the mouse from the bottom to the top of the screen (and back down again) can distract heavily from the flow of any game.
Lastly, a GUI’s purpose is to tell users all they need to know without them having to open up a menu to get that information every two seconds. This is the major reason why it depends on the game. Some games require that a mini map be shown on the GUI because you are continuously looking for items, while others do not. Each game has their own requirements.
The main thing to remember is, keep in mind what people will be looking for in your game. If you are able to interact with the item, keep it toward the bottom edge of the screen. If the item is for information, keep it toward the top edge of the screen. (I actually blame most PC’s OS for this form of architecture, but it happens to be the most effective of being the least visible for all purposes.)