Here is how I do things:

• Mass Drivers: Never
• Gas Warfare: Never
• Traditional: Rarely (planet needs to have very low population for me to consider it)
• Information Warfare: Frequently
• Mini-Soldiers: Rarely (Also not ussually available in TA, unless Drengin or Korath)
• Tidal Disruption: Frequently
• Core Detonation: Never

As a general rule of thumb, anything that damages a planet's quality is something I would never use on the grounds that I might lose usable tiles in the process. People and buildings can be replaced, but there is no way to replace planet tiles (ignoring possible bugs). Any planet I consider worth taking ussually invaded with enough troops and money to be successful in the first attempt.

Well, let's see....

Traditional: Somewhat. If I know I will win a battle and take the planet, I will use traditional. If I am broke I will use traditional. And lastly, if I don't have mini-soldiers, but don't want tidal disrupters to destroy improvements I want, I will use traditional.

Mass Drivers: Often If: my soldiering is low and enemies is high, I will use this often on high populations, but only if I am sure I cannot win (usually I will test initially a couple times to find out).

Core Detonation: Never, I will use Tidal Disrupters instead, to avoid PQ drop.

Tidal Disrupters: Occasionally If: I will use this on lower populations if I know most improvements are unusable, or if the AI has built nothing on it's planet (like Torians love to do, and Iconians... Stardock please please fix that!). When I don't have Mini-Soldiers, this is always used on subsequent invasions when most improvements will not stay/or planet is empty.

Mini-Soldiers: Very Often if: my soldiering ability is about the same, you can still consistly take out about 3+ billion troops with 1 billion. The 5-10% improvements destroyed is actually more like 2% according to the wiki. Most commonly used on subsequent invasion if Information Warfare fails, or after Mass Drivers are used to lower population.

Gas Warfare: Absolutely Never. I see it as a somewhat worthless invasion tactic for the cost. Advantages are not big enough to offset the cost and the possible PQ drop. Not the best tactic to use on high populations or mid populations. That only leaves low population, and your better off going traditional in that case. (imho, anyways).

Information Warfare: Common if: the planet has a high population and low-mid morale. Also, if I have the money to blow (which I usually do). This is only used during initial invasion, very rarely on subsequent invasions.

NOTE: on Information Warfare, I noticed that when I invade an evil civ and use IW, if I do not win, that evil civ (the Korath in this case) gains some of it's citizens BACK. After the invasion screen, say there is 2.8 billion left, and I took .5 billion, the planet afterwards has been showing 3.3 billion. I have either just never noticed this before, or never paid attn, but it happens in my current game..... Anyone else ever notice this???

Good eye.

I noticed this once or twice but never really paid attention to it...as in DivineWrath's case, it's easier to simply not lose invasions.

I'll test it if you don't test it first, DW. 

Actually, no, 2B is more than sufficient most of the time-upwards of 95%.

I did mention I abuse the shit out of info warfare, did I not?

Eh, it's cheaper/faster for me to build one transport that can hold 2B than two transports that can hold 1B...especially if I need it to get somewhere fast.  And I've been playing Breeder for long enough that population is no longer a concern to me.