Sacrificing knight for 2 pawns

Often times, I will pin the opponent's knight (F6) with my bishop after they have castled so their queen is behind the knight. They will move H7 pawn to H6 to threaten the bishop, I move bishop back to H4, they move G7 pawn to G5.

From here I can take the pawn with knight from F3 they take the knight with H6 pawn, then I take that with my bishop. My bishop is then pinning their knight and I've exposed their king by clearing the 2 pawns in front of it. 

Is this a real strategy? I sometimes have success, but I don't really have a good game plan from there. It just seems like a good sacrifice and this is a very common situation in my games, maybe because I'm an amateur? 

Sorry if this is hard to understand...

I hate when someone does that ! Lol. Now I've tried to make it a habit of placing my bishop behind my knight as a precaution. I've also heard its just a bad play to place pieces in front of pawns due to causing open files and doubled pawns.

First of all.. giving Knight for 2 pawns is not a good strategy.. Knight is valued of 3 pawns.. so.. You should never give a piece to less value.. and yes in some situations it work.. but according to me these are the points you should look first sacrificing the knight for maintaining such pin.. (a) Opponent's Bishop should not come between knight and Queen to unpin it.. (b) Opponent's Knight should not give it support .. (c) Castling should be on king side.. such that rook can't attack your bishop and then come on 6th rank to support the knight.. (d) Your Queen or any piece must attack the pin knight in next immediate move.. (e) Preferably your Rook must be on f file and you must open it in next moves..

That's not a sound sacrifice, I'm pretty sure, at least not unless Black has made a mistake to justify it, like 1-2 lost tempi or a badly misplaced unit. With correct play, Black will simply win the endgame if you make that sacrifice.

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(p. 139)
      CHAPTER FIVE

Blunders and
Boomerangs

For our combinations to work, logic dictates that our position must possess
an advantage of some type. Sometimes an advantage is simply not so ob-
vious and we must consider another way to justify our sacrificial inten-
tions: Combinations are a way to punish our opponent for having made a
mistake. Let's ponder the following situation in which chess players often
find themselves. We've spotted an exciting sacrifice that seems to be dic-
tate by the needs of the position. However, the complications to be calcu-
lated seem too hard to work out. What should we do? Go for the glory and
trust in our fate? Alternatively, should we settle down for a moment and
consider the moves of our opponent. Has our esteemed, honorable com-
petitor committed an error of some type which justifies our combination or
not? If the guidelines of general strategy haven't been trampled, there is a
very good chance that our combination simply will not work. This con-
cept, however, cannot be taken too far, especially if we find ourselves
deep into the game. Such a method of reconsideration is unusually reserved
for the opening phase. When we uncork a combination during this phase
of the game, we either have a tangible advantage in development: superior
mobility, force, space, and so on. Something is in our favor! Alternatively,
we are punishing our opponent for having neglected an important nuance,
(p. 140)
such as prematurely castling into a Bishop Sacrifice. Our opponent com-
mitted a mistake! If neither, we will likely fall victim to a combinational
boomerang, where the hunter becomes the prey.

Seirawan, Yasser. 2006. Winning Chess Combinations. London: Gloucester Publishers plc.

Great, thanks so much for that information and your analysis seems spot on. I think I have success when the opponent is either bad, or the situation you posted comes to pass. I have so much to learn! I've gotten into the 1600s playing blitz only, but I really don't have as much strategy as just quick playing and decent to sometimes good instincts.... 

You are welcome :)