Surprise and Ambushes

I have been thinking about this for a bit.  At on point I wrote a section covering the basics of surprise and ambushes since they are related.  But what I wrote, upon reflection, is missing something.  And while I understand it...I doubt that others would not.  Especially those that are new to RPG's.

So I have been thinking about surprise and ambushing again.  But it is a hard thing to apply rules to if you think about it.  The reason is how the skills are set up and how certain skills can apply to different situations then intended.

An example: Your setting up outside a a door with your team.  Once ready you kick in the door and charge in yelling at people inside to get down.  This is a tactical application of surprise, but can not be considered an ambush.  May be...

Example 2: You and your adventuring group are hiding off of a road in the bushes.  Their target is coming with in range with a number of guards.  When they are right in front your team jumps out and take the initiative killing three guards before they can put their hands on their weapons.  After a short fight, the guards are dead and the target is in custody.

The thing is how the skills apply to the situation.  For the first example, the skills used are more tactical and related to strength and the body.  While the second case relates to stealth and quickness, the ability to stay quiet.  So how do I apply this to the myriad of situations that can occur.  Hurm...