Defensive Postions: Even the strongest military defenses can be overrunned. Or just simply bypassed. Now matter how "great" your defense are, there is always a way to beat it. Never pay too much attention to one given area. Be aware of where things are and what is happening around you at all times. Don't over stretch yourself. Know what your objective is. Protect the M-COMMS!!!!
Break The Will Of The Attackers: Once you have your enemy figured out and you know his plans, use it to your advantage. Find his weakness. If none is visible, create one. Take the fight to him on your terms. Fight him where YOU want to fight. That means forcing the attackers into an area that suits your defenses. But stay aware of the status of teammates and objectives. But most importantly, not every man has to counter-attack. One squad should be back near the objectives.
Be Reletentless: Your job as the defenders is not to break nor bend. Doing so could cause your team to loose the battle. Always keep hitting your enemy hard until they quit fighting or can't fight back.
Never Ever Quit: Never say it is over until it is over. Any attack can be defeated. All it takes is one team's ability to adapt to the ever changing situation that is war that can turn the tide of the whole battle.
The "Tactical Withdraw:" When defenders get overwhelmed, sometimes it is best to fall back. This is called the "Tactical Withdraw." What you are doing is leaving that area for a better defensive postion and regrouping forces to either brace for the next **** or counter-attack. This can also give you more time to wear the attackers down and grind the **** to a grinding dead halt. Then you can push them right back where they came from. Always think about routes you take when you attack that base on that map. Someone else might know that route too.
Final Thoughts: Always remember that the wars in Battlefield Bad Company 2, or any other Battlefield game is won by hard fighting soldiers on the ground. Those that never quit are often rewarded with victory.
Feel free to add any points you feel might have been left out.