Ok, so you want to play Weapons Cache, the greatest map in the game? The map that tests your long range shooting, 203'ing, nading, and CQB skills? Always remember the key to Weapons Cache: speed.
DEFENSE
You probably want to go either north or shipping/receiving. Mid
usually isn't a problem because there will usually be a small group of noobs in the warehouse, but you can adjust depending on what OPFOR is doing.
North-
If you're in B team, you should probably go north. Usually too many people go S/R and those 4 B team spots are vital for success at north. If the 203 isn't that good, on your way to elevator toss a nade out window and aim for the trucks near s/r, usually good for a kill or 2. Head down ladder and jump when you see this colored line near the bottom, you will get there faster and won't get hurt. A good tip to get down ladder faster is if you are rifleman, turn from single to automatic before you haed down shaft and while you change you'll skip half the rungs. When you're in north, there are 3 things I usually do. Either cook a nade immediately and toss it through the half open door, toss a slightly cooked nade down the first bend and run to check the middle door, or just rush down the hall and catch everyone offguard. Switch up your tactics to keep enemy on their toes. After the initial rush is stopped, toss a couple nades down hall and then go out door and flank. Keep an eye out for 203 campers outside, if there are any just turn around and help out around the warehouse. If you are faster than the enemy, you can stop a north rush.
S/R-
The best way to kill S/R enemies is to rush at first, then pull back. Rush through S/R some rounds, remembering to jump down the stairs for speed, and others hurry and toss a nade into s/r before they know you're there. A good S/R rusher can stop both these, so sometimes its best to fall back and lean around the corner, watching the stairs for a crazy rusher. When you feel like mixing it up, its best to fall back to to the room next to the rack and toss nades into the hallway. Be quick, and watch for the rushers who try to catch you off guard. Lying prone on the rack is an old tactic, but it works and most people won't expect it any more. S/R is harder to defend than north.
Hope this helped, I usually go north for the easier kills but somebody has to help out at S/R