BF2 Demo Tips and Tricks
Either this was all really obvious, or they really didn't say these things.

The Battlefield 2 Demo came with only in-game instructions that did an OK job of teaching you to play, and limited support in a readme.txt; simply put, it was not enough. This should get your game running smoothly and open up some of the not so well known features. If you see anything I missed, or that you think should be added post it in this topic and I will look into it.

Firing modes.
I had no idea how to do it but I knew it was possible because I would somehow stumble upon it from time to time. If you select the same weapon in the weapon selection list (using the keyboard numbers 1-6 is the easiest way), it switches it's firing mode. The rifles have this functionality, among a few other weapons. It severely increases your accuracy; I took out 3 people from 20 yards who had similar guns, and we were all facing and firing at each other.

Frame Rate.
The default settings get your game running at a safe mode that they are completely sure will run with great FPS. But unfortunately it looks like crap. For people with OK computers, you can get away with increasing all of the video settings except for dynamic shadows and dynamic lighting, in fact turning them off completely will spare you quite a lot room for other video setting enhancements without effecting the visuals too much. Even people with great computers should think about turning dynamic light/dynamic shadows down if you are experiencing any lag, they are real resource hogs. I recommend lighting (not dynamic lighting which is different) be set to high if you have a directx 9 compatable card, it enables normal maps on both static and dynamic objects. Finnally, texture quality should be left where it is defaulted to, as increasing it usually results in video memory being swapped in and out as you are playing.

Commander/Squad Leader Menu
I had no idea that if you hit ("Caps Lock") there was a complete control panel for commanders and squad leaders until at least 12 rounds. While you are a commander, you can zoom in to the real world scale and actually see what is happening in 3D. While you are a squad leader, it acts as a normal map of the level for you to direct your squad. Not going to go into much more detail with this, just revealing the fact that there is this menu.

Radio Commands
It wasn't that difficult to figure out but I was wondering why F1-F8 weren't doing anything...the new radio commands come in the form of a single key ("Q") which while being pressed brings up an in-game menu allowing you to move your mouse to select a radio command. There is no pointer, it just highlights the commands. It automatically decides what commands you will need, and they apply to where your reticule is focused. The default selection is spotted in most situations so reporting something you see like a helo is as simple as hitting q and clicking the left mouse button, no more individual report keys as it figures them out on it's own. While you are a commander, squad leader, or in a squad you are provided another menu to request artillary, supplies, new orders, UAVs, and for squad leaders only a squad instruction set of commands. NOTE: While not a commander, the requests for UAV, Artillary, and Supplies are sent to the next person in power above you.

C4 sticks to vehicles
When you are special ops, you are provided C4 which I did not know until today, sticks to most vehicles. Right click to bring up the detonator.

Flares/Smoke
Most vehicles are equiped with smoke or flares (for ground or air.) Flares deter guided rockets, smoke just hides tanks and such. The ("X") button fires both smoke and flares depending on your vehicle.

Let me know if you benefited from this, or if I am just blind and all of these things are obvious!