Here's a quick guide to the weapons
http://xbox360.ign.com/articles/859/859204p1.html
and vehicles
http://xbox360.ign.com/articles/859/859204p2.html
of war in the Battlefield Beta:
Bad Company Weapons
Assault Rifles
The general purpose weapon of the Assault class:
*Effective at all ranges but dominant in none.
*Firing in bursts will maintain accuracy, and use the sights to zero in for a headshot.
*The underslung grenade launcher that's fitted as standard on all Assault rifles adds destructive capability, and helps keep enemy heads down.
*Rates of fire and damage will differ with each model; find the one that suits your style best.
Sniper Rifles
*A superior long range weapon, the Recon class sniper rifle is unmatched at range.
*Demanding patience and a steady hand, zero in for the one-shot kill.
*Bear in mind that at extended ranges you may need to lead your target to score a hit.
*There are 2 main classes of sniper rifle, bolt action and semi-auto – one packs more punch, while the other will allow you more rapid fire.
*And try not to get caught in close quarters -- firing from the hip doesn't suit this gun.
Shotguns
*Unmatched in point-blank efficiency, the shotgun deals massive damage at extreme short range, as fitting the Demolition class.
*Designed for quick reaction shots, zooming will yield only minor benefit, but the cloud of pellets more than compensates for any lack of accuracy.
*Don't try to go toe-to-toe with snipers – the effectiveness of the shotgun declines rapidly at range.
*Choose between pump action or semi-auto versions.
Submachine Guns The Specialist class silenced submachine gun has the highest rate of fire of any weapon.
*Specialising in close quarter combat, the SMG nevertheless retains some effectiveness at range.
*Fire in short bursts over distance but let rip up close -- watch your ammo levels though, you'll eat through magazines in no time.
*Rates of fire and damage differ for each version.
*Love ain't the only battlefield.
The Light machinegun is the support class weapon of choice, specializing in laying down large amounts of concentrated fire.
*If you need to pin down an enemy at mid-range, this is the gun for you.
*With all the shaking from firing the weapon, it's not the most accurate, but sheer volume of bullets will counter that.
*Watch out for low ammo levels – the gun is heavy, so reloading is time-consuming, make sure to pick your moment.
*As with the other automatics, rate of fire and damage will vary for each.