Ok, this was a pattern that could have come up in one of my recent games, but didn't. (I've slightly altered it for this problem.) As before, there are several moves for black that deal with the threat, so the solution will show what happens if black doesn't deal with it.
This way of seeing threats is working for me. If White had one free turn in puzzle post #42, it becomes quite clear that Black loses quickly by force. Good stuff.
I often evaluate my threats by asking what happens if black just passes his turn. Once I do that, I go back and ask what he can do to stop those threats. That's a good way to cut down the number of moves you need to calculate if you know exactly what he needs to prevent. You do have to be careful of zwischenzugs during the combination though.
Threat Puzzle No. 6
White is having no fun in the Pirc Defense after 1.e4 d6 2.d4 Nf6 3.Nc3 e5 4.Bg5 (?). Black hits White with 4…exd4 (!), and the position goes from slightly better for White to 100% equality. This time the threat is easy to see, useful with new students, especially for one of mine today. “Why are you exchanging your knight for my pawn?” Arg!
There are two good moves. Click on "Move List" to see the variation. Which one do you like best?
Got the first one immediately, in several variations the same threat applies. The second one took a bit longer, but got that one too. The third one also took a bit, but I like it.
In order to not give anything away accidentally, highlight below to read what I found:
1. ...Rxd4 Rxd4 Ne2+ fork picks up a pawn and effectively isolates white's c5 pawn.
2. ...Nd4 threatens to win f3. The only good defense was with the knight, but that then allows a discovery on the king if white plays Ne1, so he has to try defend with the king, but Nxf3 Kxf3 Rxd3+ still wins the pawn.
3. Nf4?? Nd2! counterattacking. If Nxd5 then Nxc4+ Kd3 cxd5 protects the knight, and white can't penetrate, or protect his c5 pawn, and will lose. If instead of Nxd5, the game goes Nf4 Nd2 Rc2 then exf4+ also comes with check forcing Kxf4 and black can save his knight (..Nb3 perhaps) and remain a piece up.
Is this what you had in mind?
I caught the 1st and 3rd puzzles tactics within a few seconds (3rd might have been hard in a real situation though with no one telling me to look for a win),
but was too tempted by a bind In puzzle 2 thinking that your tactic would be to trade into a rook endgame and win the c pawn which led to an advantage, but still unclear with black's king cut off IMO so I didn't think a good solution. Lucidish points out the win of the f pawn though, which seems a much cleaner win.
I was thinking Nf4 with Rd4 and Ne6, black will win material and white is all tied up. I tend to look for binds before tactics because I'm a sadist 
Wow I just put this into Houdini and it likes my line with Nf4, Rd4, Ne6 idea! Not it's first choice (I didn't find white's best defensive moves) but still :D My idea gives black a clear advantage.
It found a defense to Nd4 by the way which I didn't see at all, white just plays f4. It also agrees the endgame isn't clear if all you do is grab for the c pawn, reading =
Does it want Ng5 instead of Nd4, or am I just totally wrong?
Houdini is showing me 1...Nf4 with Rxf4 as the best defense, it walked the king up the c file a bit and the knight picks up the pawn so not a pure exchange sac but it says black is winning.
I'm my line if white defends with Rc3 it likes g6 and the rook may even go to Rd7 to come in on the b file but Rd4 is still good it says. I'm not letting it think very long mind you, like 10-20 seconds for a move
Rather than using puzzle format I will post some diagrams for discussion.
Black to move. White just played 7.Ng1-f3. If White had a free move, what would he play? Consequently, what should Black do to avoid this? Another important question to ask yourself is this! Do I need to worry about this threat or can I allow it? (In this position it's sort of okay to allow the threat but most players prefer to prevent it!)
I like this format! I didn't take a look at any of the discussion on this diagram, so it feels like a real chess game, and I need to make a good decision.
White has two bishops free to roam on excellent diagonals. It makes me want to play 1.e4 2.d4 everytime I get the chance. Black seems to be in a real pickle.
If I were White and had one free move, I would not hesitate to play h4-h5, threatening hxBg6.
Can Black ignore this threat? Well, Black can retreat his bishop to h7, but why not develop a piece and play Nf6? Let's see. 1...Nf6 2.h5 Nxh5 3.NxNh5 BxNh5 4.RxBh5, and Black loses the exchange. Perhaps better is 1...h5, preventing 2.h5.
Yes. I really like this format. Well done. You pumped life into Looking for Trouble. Thank you. 
Regarding puzzle 47, I don't know what Black's idea was behind the rook check, since it didn't place White in zwischenzug or zugzwang. Too advanced for me, but I did try.
Great puzzle!
Nice puzzles
Keep em comin!!
I like solving challenging tactics puzzles...
That 2000 one wasn't that hard though-i got same solution as bc you knew there was a win.
Any more Expert+ lvl problems?
Ill contribute one. Its not my own though. Its from the CB magazine #141-white to move
Got the first one immediately, in several variations the same threat applies. The second one took a bit longer, but got that one too. The third one also took a bit, but I like it.
In order to not give anything away accidentally, highlight below to read what I found:
How do you place an invisible comment in a thread? Yet another improvement on the topic - Looking for Trouble.
@ Lux and ajedrecito - A big thanks for what you have done for this topic. I and Dan Heisman will be most happy.
I wasn't completely satisfied with my format until these improvments. Both the discussion/diagram format and the invisible comments concept are absolutely brilliant. Thanks!
Now I feel confident in adding more content to Looking for Trouble.
The way I did the "hidden comments" was to type them normally, then highlight them and change the text color to white (use the button to the left of "Font size")
While it doesn't exactly match the background at least on my screen, it takes effort to read it, which is good enough.
I think I got the first puzzle in #48.
"In the game, White played 27.Rg3?!. What did he miss?"
27.Rg3?! Rxd4 28.Rxd4 Ne2, triple forking Kc1, Rd4 and Rg3.
Highlight the white text above to see my answer.
The next two puzzles in post #48 are way too hard for me. Dang! Chess can be brutally complex!
That's one of the big reasons I like chess.com's tactics trainer. It doesn't tell you what to look for. Sometimes it's a mate (in how many?), sometimes a piece, sometimes a pawn, sometimes your best bet is stalemating yourself.
1. You're absolutely right! But naturally we know what to look for when we're told something is there.
2. For this reason I really like Karsten Muller's new book from ChessCafe Puzzle books series #2: Test your positional intuition. It has a lot of positions where there is a tactical solution, but it doesn't tell you where they are!
If you don't know what to look for, start by looking for checks, captures, trapped or loose pieces(yours and your opponent's!), and then consider how to follow the plan you have hopefully set forth for yourself, or counter your opponent's ideas if they need to be.
The point of tactical exercises is to learn the patterns so you can use your pattern recognition ability to deal with tactical confrontations.
1. Who? Did I get something right. 
2. ChessCafe is awesome. Besides everything else, for me, it has the Novice Nook. Does Karsten Muller write puzzle books for all skill levels? I'll check it out, anyway.
Update - Indeed, GM Karsten Müller has authored a remarkably readable positional primer for intermediate and advanced students of chess. - GM Susan Polgar
Intermediate to Advanced would not be for me. Beginning to Intermediate would be best.
I don't like chess.com's tactics trainer because there aren't any difficult tactics. The trickiest thing I've seen is something like Black pawn at a4, king at a1, White knight on b4, king on c2, white to play and mate in seven (if my mental count is right) because you have to find about one slightly counterintuitive move.
Test Your Positional Intuition is the only puzzle book I got (as a prize) and it's probably not appropriate for players below Class A or Expert level.
Geez! My chess.com tactics rating is only 1206. None of the tactics puzzles I've peeked at over 2000 make any sense to me. I simply can't find the tactic, no matter how long I take.
My tactics trainer rating is now hovering right around 2000, so I still have plenty that I don't find easily. Perhaps once I've exhausted this tactics trainer of hard problems I'll look elsewhere, but it's doing fine for me for now.
Ok, this was a pattern that could have come up in one of my recent games, but didn't. (I've slightly altered it for this problem.) As before, there are several moves for black that deal with the threat, so the solution will show what happens if black doesn't deal with it.
This idea was taken from a game of mine, but I altered it quite a bit to make it more forcing, so my apologies in advance if there's a flaw.