Great expectations

Me and a friend are a duo soldier combo in our clan.  Do you know any two-man soldier tatics.  For example, one man takes out a sentry while the other kills the engineer or the regular camping pyro\demoman or back to back at well at teh middle point.  We have other ideas but we just want to hear from others as well any advice is appreciated.

One go left one go right and juggle people into one another?

It works pretty well as I pyro.

I play soldier in a clan and sometimes together with another solly.
However, I dont think we cooperate in that tight way that you are describing very often.
We usually have one defensive solly that concentrates in protecting the medic and another more offensive one.

Of course, if one of us is shooting at a target, then the other one try to assist him so that we may kill the target easier and faster, especially if the target is a hw.
Of course, two sollys would be nice if you want to kill a sentry, since one is not usually enough if you face the sentry from the front.
However, sentries usually get wasted during the uberrush anyway. 

I would say on ctf maps, one defend the team's intel while the other one help pushing the offense forward and might even take the enemy's intel?

But on capture point maps I don't see many soldiers would cooperate and use any tactics at all...they usually would seperate and cover more areas of a map..