building an opening repertoire around D4

Who are you guys playing? I have never seen a player OTB 1800-1900 that doesnt know his openings, and know them fairly well usually.

Better then me certainly.

I may just be an outlier because openings have always been the worst part of my game, and I usually come out with a disadvantage. To me all my opponents are opening gods.

I just played and lost to a 1800 guy last week, I was out of my opening knowledge at move 2. I asked him after the game what the opening was, and he replied "The London". He had been playing it apparently for 10 years or more, and knew it well. While the opening was not a disaster for me, he pointed out an elementary opening error I made in it regarding his bishop.

It could just be everyones strengths and weaknesses are different - I was lecturing people 200 points higher than me about the endgame and exactly which Queen/pawn endings were drawn and which were wins, and why. I feel great in endgames. Openings - I need lots and lots of work. If I can improve the worst part of my game and make it my best, I think I will improve quite a bit. We could be talking past each other because of a different idea of what constitutes iopening knowledge. Maybe being out of book on move 2 is not what you guys are referring to.

I just google the stuff I'm unsure about and end up finding articles with annotated games. That's how I make a lot of my choices: http://www.chesstape.com/index.php/advanced/telljohann-vs-adams-london-system-2013-gibraltar-festival-rd2 You can't go wrong with Mickey Adams in these positions. 

But anyway you can find a lot of annotated games by just searching for things you aren't sure about. Anotated games would probably be helpful as you can learn a little about openings and a lot about middlegames.

That was pretty impressive. He made it look so simple.

yeah if you look at that game, after whites 4.e3 he always has to be concerned about a Nh5 manuever from black. I exchanged my c pawn for whites d pawn, which was the mistake I mentioned in my post above, because this allowed white to recapture with the e pawn and give his bishop an escape path.

 Obvious, looking at it now. But with the clock ticking in unfamilar terrain for me, I missed that. My opponent, of course, was very familar with the ins and outs of this setup.

Finding a good time to capture can be tricky. There's a system against these queen's pawn openings where Black plays ...Nf6, ...e6, ...c5, ...b6 and there he actually does capture on d4 early in the opening. I never understood why.

I think there are different themes at work here. There is "book" and then there is sort of "principles and common sense."

To me I guess they need to grow and increase more or less together. For instance, lets say I choose the Nimzo indian as my main defense against d4. Fine. So I have to start to "book up" on whites answers to 3..Bb4. The two main branches are Qc2 and e3. So I have to try to have an approach to those branches etc. The part I memorize or know would be my book. At first the book will be pretty small and you get thrown onto your own resources quite quickly and you have to wing it with your common sense and principles etc

Obviously the more book you know, the better.

So for my nimzo example, 1.d4 Nf6 2.c4 e6 3.Nc3 Bb4......what if he plays 2.Bg5 (Trompowsky attack)....what if he plays 2.Bf4 (some type of London)

eventually I will see those replies and at first I might be clueless as to what to do but after the game I can look them up and at least know a few decent moves to play against them. Usually a stinging loss is a good motivator

Did you look up any opening lines after the loss?