Tips: 
When attacking, go for the outer extremities. Much of the weapons are in the arms, try to take out the arms to minimize your damage. On mechs that don't have jump jets take out a leg (that will immobilize them) and then move behind them to finish them off.
Make use of the zoom feature. You can often spot powered down mechs from a long distance away. Then you can use long range weapons such as PPC to damage or destroy important systems.
Master DFA (Death from Above)
Try to equip every mech you use with jump jets. They can not only save your life when a leg is blown off. But they can be used for a quick burst of speed instead of using the MASC system.
If your targeting camera is damaged switch to enhanced imaging mode to see the damage of the enemy mech.
The enhanced imaging mode is useful for keeping an eye on your damage since you are able to see your body damage also.
Using a combination of two PPC's and lasers you can imobilize almost any mech you encounter.
Downloads:
Download three cool videos of MechWarrior 2.
