OK, big SPAM of the BF1942 Tips and Tricks section of the official site, which is located in a hard to find and terrible to navigate spot. Forgive the length, but it's big, and HIGHLY useful:
Land Vehicles
When driving the tank, take out foot soldiers with your co-axial machine gun
by clicking on your right mouse button. This allows you to fire the machine
gun without exposing yourself to return fire.
Damage takes armor and angle into account, so shoot tanks from the sides or
behind at a perpendicular (90 degree) angle to maximize inflicted damage.
But remember, shooting at the frontal armor will only cause minimum damage.
Artillery can fire further than any other vehicle. Use the increased range
to disrupt enemy movement from safe distances and use snipers to scout enemy
units.
Remember to use [C] or [F] keys to change views while in vehicles. Use them
to occasionally look behind you when in vehicles, especially tanks. Tanks
can be destroyed with one good shot from the rear.
The scout car can be used as a bomb if driven correctly. Just aim it at a
tank or other target and hit the accelerator. Don’t forget to jump out
before you hit. You can also run over infantry if you’re going fast enough.
The APC will heal and resupply you if you sit in the back.
Be careful driving over rough terrain, if you’re going too fast you can
damage your vehicle.
You can drive over landmines if you go slow enough. Of course you’re a
sitting duck while you navigate this way.
Air Vehicles
Zoom and Scoop -- This maneuver is for when you're in a dive-bomber and have
an empty backseat. Fly very, very close to a ground-based teammate. Have
your teammate hold down the enter vehicle key [E]. If your teammate is close
enough, they will pop into the rear seat of the bomber for a quick getaway.
This is really useful in CAPTURE THE FLAG games
Drop torpedoes from planes at a low altitude or they might go under the ship
you are targeting.
Use the [F9] key to toggle your plane's HUD (heads-up display) on/off. You
can fly planes with arrow keys (as default) instead of mouse.
If your plane is about to crash, hit [E] to eject and [9] to open your
parachute.
Planes are probably the deadliest vehicles in the game. They can blow up
tanks with one well-placed bomb. Create your own multiplayer game and
practice bombing vehicles. A good bomber is a valuable asset to any team.
Joysticks help A LOT when flying, try binding your yaw and throttle to the
keyboard, but leave the roll and pitch to the joystick. Remember to stay
away from the AA guns!
You can resupply your planes by flying slow and low over airfield/carrier
ammo sources. You’ll know you’re near one if the ammo icon appears on your
screen.
Airplanes are weakest in the engines... shoot for those in dogfights. Just a
few well-placed shots can turn your opponent into scrap metal.
Watch for AA (anti-aircraft) and machineguns... they can turn your plane
into swiss cheese. To avoid these, approach them from below their horizon
and drop a bomb on them as a wake-up call.
The B-17 is as slow as a pig... but it can lay a devastating carpet of bombs
on the ground. With two gunners to keep fighters off of you, this is a
potent weapon. Your gunners can also act as paratroopers.
Infantry
Short bursts produce higher accuracy than continuously holding the FIRE key.
Firing while standing still, crouching, or prone also helps with accuracy.
Pay attention to uniforms. When you first spawn, look at your teammates'
colors. Usually one team's clothes are darker than the other. Sometimes the
player tags don’t show up quickly, so pay attention. DON'T KILL YOUR
TEAMMATES!
When using the sniper rifle, hold the FIRE button down after you shoot to
stay in zoom mode. This will allow you to see how your shot fell. When you
release the FIRE button you will un-zoom and reload.
The scout can place cameras with the binoculars fire and the artillery
pieces and ships can cycle through those cameras with [ALT] + FIRE.
Right mouse click when you are on foot for a slightly magnified view.
Shots are not instantaneous; depending on the distance you may need to aim
in front of a moving target. Experiment to find the correct adjustment for
all your weapons.
You can throw grenades a short distance with [ALT] + FIRE.
Choose your kit wisely. Just because you like sniping doesn't mean your team
can survive without a medic.
Increase your grenade's distance by jumping when throwing. You can throw a
grenade about a block and a half by doing this.
Learn to use the environment as cover, hide behind trees/rocks/buildings and
don’t shoot until you see the whites of their eyes (you won’t give away your
position, and you’ll have a better chance of getting an easy kill).
Tanks are easily outflanked by fast moving foot soldiers. Always attack
tanks from the rear. Throwing grenades beneath the tank is also effective.
Land Mines are effective for closing off areas to tank and vehicle movement.
Remember to tell your teammates where you place them.
Watch your ammo and health: Grenades may be great for killing enemy
soldiers, but unless you're an anti-tank or engineer soldier, they're your
only weapons against enemy tanks. Remember to reload whenever you see an
ammo box and heal whenever you see a medical locker or APC.
Teamwork is your key to winning and getting a good score: Try working as an
anti-tank soldier or engineer with a friendly tank. As he distracts them in
the tank, you can get around them for the killer rear shot or plant some
dynamite. Afterwards, you can repair your ally. If quick travel is
necessary, he can give you a ride. Type a quick message about strategy, and
don't assume he heard it unless he responds.
In concentrated street battles often reloading is too slow. Try switching
kits [G] with the guy you just killed!
As a medic you can also heal yourself.
When in a firefight from a distance, STAY LOW. Go prone or keep moving.
Naval Units
You cannot command enemy ships. But you can steal the airplanes off of their
carrier.
Submarines go slower under the surface so drive long distances at surface
level and submerge when you spot a target.
The destroyer is your only means of sinking a submerged submarine... keep
them near high-priority targets to sniff out those sneaky submariners.
Watch for the submarine’s periscope. Use radio commands to notify your team
when you’ve seen it. That will give everyone a general idea of where it’s
located.
The pilot of the destroyer can drop depth charges with ALT+Fire. The gunner
in the rear turret can use the guns in indirect fire mode if a sniper calls
for artillery.
Watch for the shallow water. The bottom will rise abruptly as you approach
dry land. Try to avoid beaching your ships.
The battleship can use its guns in indirect fire mode if a sniper calls for
artillery.
Ships can take a lot of pounding... but just a few torpedoes will sink you.
Watch out for submarine and torpedo bombers.
All ships except the submarine have landing craft attached to them. These
can be used to make landing assaults.
The ramp on the landing craft is lowered/raised using the up/down arrow
keys.
Miscellaneous
Axis nametags are ALWAYS red and Allies are ALWAYS blue. Remember that.
You will see teammates in your minimap as the color of your current team:
BLUE for Ally and RED if you’re Axis.
Strategy. Don't just run, blaze away, and die. This isn't your standard
first-person shooter, and that will get you killed. Think, aim, move, fall
back, repair, get healed, and backup your teammates.
Man the shore batteries to keep the ships at bay.
Use 16-bit color for better framerates.
Experiment with your sound settings for a better framerate. Also see if you
can use hardware acceleration.
Don't win the fight but loose the battle. Remember to focus on control
points in Conquest.
Memorize and use the radio commands.
The direct route to an objective is rarely the safest; use alternate routes
to achieve goals. Be sure to watch the spawn interface when you are dead, be
prepared to click on a new spawn point if yours is lost, because you don't
want to wait for another spawn cycle.
Choose your spawn points wisely. Examine your map before spawning, look for
vehicles, and look for places that may be spawn-camped by the enemy. Do you
want to defend or attack? Where is the fighting concentrated? Do you want to
join the main battle or execute a backdoor strategy of your own?
Learn how to use all the weapons at your disposal effectively. Each hand
weapon and vehicle has strengths and weaknesses.
Try your best to respond to your teammates' radio commands. If you're an
anti-tank soldier and you hear a request for anti-tank support, look at your
minimap and see who's talking -- they’ll flash yellow.
If in a conquest game and the spawn point aren't changing flags, look around
for the enemy who might be nearby preventing it.
Keep your eyes open. Snipers, landmines, expacks, and artillery are silent
killers. ALWAYS look out for these.
Vary your class to fit the situation. If the enemy is not using tanks, don't
play an anti-tank all the time. If your team is mostly on foot, be a medic
and heal them. If your team is in tanks, be an engineer and fix them.
Supporters are every bit as important as attackers and defenders.
If you catch an enemy from behind at a distance, don't shoot right away --
you may miss and alert him to your presence. Close in a bit and make it a
sure thing.
Empty vehicles that are nearby will appear on your minimap as gray icons. If
one of these disappears abruptly, you know an enemy has jumped into it.