Direct Damage

The direct damage approach works with interventions and/or programs. Prime suspects here are the 7th Cavallery Air Strike, Surgical Strike, Crash&Burn, Corrosive Mites, Termites, Digital Pyro and similar programs and interventions. Attacks like this are inherently hard to block or circumvent since you usually don't know what is going to hit you and there are only a few cards that can work against direct damage attacks. Core Freeze (Def-R) stops program attacks cold but has a 15% chance of leaving play each turn and Core Shield (Def-UC) prevents direct damage programs of being run in a certain city. It is much harder to stop direct damage done by interventions. World Conference (Def-UC) stops non-UN interventions, but only for 5 turns. Military Clampdown stops FUS interventions for 6 turns. However, there is no way to avoid damage to your base if one of those direct damage cards are used (unless you run a Wormhole Shield and that tends to eat you up in a matter of turns itself).

'Normal' Damage

Normal damage is damage that is dealt by assets. This approach has one obvious shortcoming - assets can be blocked. There are two ways to deal with the threat of being blocked. One is to ignore possible blockers and overwhelm the defense by brute asset force and the other opens a whole can of what are called 'evasive techniques'.

Brute Force

Brute Force attacks are easily to recognize: Exo Troopers, Enna Tung, Utopia Gunships and other huge FP assets are used to simply stomp over any defense that is present at the opponents HQ. This approach tends to be very limited without any supportive actions taken, since the biggest attacker will eventually fall prey to the umptenth Bion Guardian produced by a Bion Pod without dealing any damage to the main target (if you are lucky you deal 1 damage vs Blinder Cannons). That's why you want to use cards that assure your assets to go in for the kill.

Evasive techniques

Evasive techniques are accomplished through supporting cards to avoid contact with possible defenders. This spreads a variety of cards such as single asset eliminators (like Taser Shackle, Orbital Cannon Strike or Slaver Raid), multiple asset eliminators (Napalm Strike springs to mind, also UN Warcrimes Tribunal). But instead of eliminating possible defenders completely it is often cheaper and quite as effective to just deal with them temporarily to send assets unblocked in for the kill. This is often called a 'gimmick attack' and a prime example for this would be Scatter Hack. Other cards in that category are EMP Strike, False Alarm, Presence of Ty'llin, or even Brain Candy and Dial Static. To avoid defensive interventions like Peace Keeping Force, Laser Defense Grids or defensive Napalm Strikes, it is wise to include cards like Account Freeze to stop such actions for the duration of that critical attack. I.e. Scatter Hack + EMP Strike pretty much clears all defense (after that only Bion Pods and Viral Vines are still standing), an additional Account Freeze will stop the Pods, LDG and interventions (unless you opponent packed Emergency Cash Funds :). For a similar effect Presence of Ty'llin and Scatter Hack will tap or move everything but Mindslavers.

Conclusion

The most effective decks that are reigning the battlefields today combine several of these forms. Big Stupid Military uses Brute Force + Napalm Strikes, DHQ/Speed uses DT, EMP Strike or Scatter Hack as support. The evasive technique of Radiation/Tribunal decks should be pretty obvious. The key to winning, as someone (I do believe it was Ian) once said, is to fit your deck with a pointy end and then stab your opponent with it and the evasive part is there to make that stab count. Go for it!