Well Pikachulord6 from what limited expereince I have with this is, as it has been pointed out the trick is in Whites second move. Most who start with 1.Nf3 are less inclined to attempt 2.e4  (which does not mean it can be fully ruled out of course) and will play either c4 or d4:
Correspondence:

and over the board:

and when e4 does comes try to do better than this:

Maybe these games are not the best (being back then) but over the years I have managed to push my ICCF rating past 2100 since then. All I can say is If you are going to attempt 1.Nf3 h6 then Basman's "Killer Grob" is worth a read as is his "Creepy Crawly Opening" booklet. As one other thing you can might want to look at is Mr. Buckers archive section at Chess Cafe because if one's memory serves me correctly you should find a very good article on 1.e5 c5 2.Nf3 h6 which is pertinent to what you have asked.
Regards
Hadron.

My thoughts:
1.Nf3 - The first player wants a complex game going through some transpositions where he can outplay his opponent..
1...h6?! - The second player says: "Bang! You're out of theory! Yes, you have += right from the start, but let's play chess!"
2.e4 - White wants to punish black for such an unsound move. And the best way to do it is to enter an open game.
2...e6 - "Ïf I play 2...e5 or 2...c5 we can enter an open position and my 1...h6?! can be a loss of tempo that really matters.. 2...d6 can be considered to, but the h6-pawn wouldn't fit too much in a possible Pirc setup. 2...c6 is an option of course, but in Caro black can't develop the king side as fast as possible."
3.d4 - White builds a strong centre.
3...d5 - The only possible continuation after 2...e6. 2...c5 is riskier. And white can't play Qg4 in a possible French type position because of the knight on f3. Now 4.Nc3 can be met by Nf6 and black is OK. The pawn on h6 prevents Bc1-g5 and can be used even for g7-g5, too..
Then 4.e5 or even 4.exd5 and 5.Bd3 is possible for white, but I think black will survive. 

The other approach:
1.Nf3 h6?! 2.e4 g5?! is too much for me.. Maybe Stefan will continue further with the moves..