Howdy EA gents!

So I'm going to be having a game tomorrow and I was sitting there thinking about my game in my head and wondering "what will my strategies will be for the game this time?". As it dawned on me, the last couple times I've played I realized that I haven't been paying too much attention to rear guard actions.
I tend to play an aggressive play style and tend to advance my forces to my opponent's side of the table. Although I will admit, this hasn't caused me too much of a problem as of late since my opponents never try to Blitz me. I'm thinking this topic is probably going to be a huge factor when it comes to tournament time.
So I guess my question is this, should I spend points on troop formations and try to dig in for defense or should I use something faster, such as LV to come to the aid of my objective should they be somewhere else on the battlefield? OR should I just say, "awwww to hell with it! I'll Blitz him/her instead!"

What you are asking is quite a good question - but the answer is "it depends". If you are playing tournaments, the tendency is to try to find a strategy that both fits the army and your style. So you would normally be considering
- what army are you intending to use
- what is your play style (you say you are naturally 'aggressive')
- even in a tournament game - what is your opponent's army and style
- how many formations do you and your opponent have (and what are their capabilities)
- What is the battlefield like and where are the objectives
- etc

However the first question is, what do you mean by a "rearguard action"?

To me, a 'rear guard' action implies trying to recover as many troops as possible from a table; almost exactly the opposite of the tournament game in which the aim is to advance into enemy territory and capture objectives, while preventing the enemy from doing the same things.

Definately a playstyle thing, there is no hard correct answer - I am also quite an aggressive player prefering defence through attack - so usually end up with a single 100-200 pts formation guarding my blitz.

Yeah...guess I used the wrong term huh?

Yme-loc kinda hit it on the nose. I guess I'm asking what would be a more viable option to protect your blitz. But I guess that's kind of a general question.

Oh and by the way, I lost the game...thanks to being hit in the REAR of the battle line. Good ol Marine Drop Pod from hell army. I got piecemeal-ED!

As well as depending on play style it can also depend on the Army used.

For me.
When using Codex or Chaos marines usually everything goes forward offensively and broken/battered remnants fall back to positions so they can move to hold or contest objectives, hopefully in either half if positioned well.

With Lost and the Damned usually 1 or 2 formations are garrisoned with the intention of going forward if possible or defending objectives if not. Whilst inevitably 1 or 2 formations refuse to move forward and end up being the 3rd/4th turn objective grabbers/contesters from my half of the table.

With Imperial Guard and Eldar there's usually an artillery formation or 2 (Manticores/Void Spinners etc.) which want to sustain fire every turn. Plus the formations left to guard them (sentinels/Infantry Co./Rangers/War Walkers etc) who rarely move forward and attempt to protect/contest objectives late in the game.