The meaning of development seems clear. Get the pieces out into good positions. What moves are entailed by this? And which moves are unadvisable? Let's look at some basic structures. Don't worry too much about move orders and tactics yet.
1. Two Pawn Moves
Usually the King and Queen Pawns should move. There are other options, but in every case, two pawn moves allow both bishops to enter into the game. Pawn moves are also for developing Bishops.
In this next diagram, White should play Bc4 before d3, so the Bishop is outside the pawn chain.
In this next diagram, Bf4 before e3, to let the Bishop participate.
A tiny pawn center is also quite playable.
There are Kingside and Queenside fianchettoes.
White fianchettoes the Queenside Bishop. Black fianchettoes the Kingside Bishop.
The pawn moves allow the Bishops to enter. Too many pawn moves are likely to be weakening. The Bishops end up with many ways to enter the game, but there won't be time for them to do it.
2. Knights Before Bishops (Sometimes)
The Knights have fewer viable squares than Bishops. Knights are often best posted to the most obvious squares.
Knights can go in other directions, but it is nearly always best to get them off the sides, and out of the way of the King and Queen.
The Knight visits e2, but doesn't linger there. The Knight cuts off the Queen's control of f3, and this makes White vulnerable. Two more examples...
Sometimes Knights on bad squares are enough to lose a game. The Knights take up space around the King, but don't control squares the way a pawn would. Such Knights can be worse than no piece, since they remove running squares without adding defense. In the next diagram, Black makes one unwise Knight move, which can be losing.
White mates with N@f6
Since the Knights have fewer options, it's often best to commit them before committing the Bishops. The best location of the Bishops can't be known until more has happened on the board.
In the next diagram, Bd3 is the best move. In this position, long Bishop moves like Bb5 or Bg5 only help Black unravel and expand by trading in a cramped position. The timing of Bd3 is also the best. Black commits to e6 and d5, and White centralizes the light square Bishop and also points it at Black's Kingside.
Reasonable development for both sides. Black waits for the White Knight to go to c3 in order to pin it. When Black moves the Bishop to b4, there is a clear purpose.
I witnessed one player instructively mishandling the Black pieces.
None of the moves are individually losing, but the thinking behind them creates unwinnable situations.
3. Allow Inferior Trades to Clear the Back Ranks
Let's say White mouseslipped, allowing Black to play the space-gaining ...d4 push. White wisely lets the Knight go. White lost a point in material value. In bughouse, the material values of the pieces are different, but the significance of material imbalances are also different. While White lost a point of material value, White's control of the center is huge. In fact, I think Black should not take on c3.
This is also fine for Black. Black could have saved the Knight, but what's more important is maintaining a foothold in the center.
Sometimes, when my partners get into messy positions, I urge them not to back off. "Don't back off; add more defenders." The values of the pieces are fluid, and not fully understood. But materialism comes after King safety.
4. The Desire to Be Special Ruins Games
Good moves are not optically striking, but they are meaningful. Some players enjoy offbeat lines, and they burden themselves (and their partners) with a need for individuality. I'd like to see bughouse with random starting positions. The problem for bughouse played with the traditional starting position is that any flamboyant deviations are easily identified and punished. This doesn't mean that there is no scope for individuality and creativity--there's just less scope for individuality and creativity in the initial phase of the game.
Some players like to play 1...a5?! I respond by letting the pawn go so far, and taking one move to prevent it from moving further. 1...a5 is not even that bad. But the need for uniqueness is a burden for Black and their partner. I would offer a caveat: 1...a5 might be a reasonable way to help a partner who is a beginner. By giving Rook, instead of Knight, a beginner might more easily live through early sacrifices. But otherwise, it's not great.
Really strength comes from understanding what's more familiar. If you can appreciate the strength of boring opening moves, you will find the aesthetically pleasing quiet moves in the middle game, and double-exclamation-mark-worthy checkmates. You should talk to your pieces--metaphorically.
Who would you rather have as a partner? A strong but style-less player, or a creative genius who gets checkmated? The players aiming most rigidly for individuality in the opening are the ones who can be most impossible to win games with. Real strength is invisible; you can't see how strong players would respond to various moves. That's why just looking at the moves of strong players doesn't bring improvement.
5. Modest Queen Moves, or Well Timed Queen Strikes
Getting the Queen out prematurely can make a game impossible.
Let's see a modest Queen move.
This is theory in the exchange French. White plays Qe2, which is an active but safe square for the Queen.
Let's see a well-timed Queen Strike. Something like this can be very effective.
Or this...
Even if Black gets B@g6, this can be very effective. If Black has to play another other move, White has a very nice time.
6. Rooks
I asked one partner to develop. Actually I may have been "on tilt", with many partners losing in positions like this...
If you lose a game with undeveloped pieces, the undeveloped pieces are probably why you lost. This partner, a titled player, retorted that I hadn't developed my Rooks. This was unserious. The Rooks often enter last in both standard chess and in bughouse.
The Queen's Bishop can sometimes be best on the home square, supporting pawn at h3/h6.
The Bishop hasn't moved, but it's ready to move. If it can go to h6 directly from c1, that's an efficient path. It could be considered optimal, depending on how it was brought about.
7. Play Quickly, Analyze Slowly
Speed is important in bughouse, but it isn't fundamental. Some players who can be called "speedsters" only play fast, but get into positions no amount of extra time can fix. Move quality and partner coordination are more fundamental than speed.
If we revisit the above example where Black played two Bishop moves and no Knight moves, we can find a moment worth trying to fix.
What is Black aiming for, or afraid of? The place where a principle was ignored is the place to look for improvements. As we saw before, Black would be better off moving the Knight, even if that Knight is lost for a pawn. Although saving the Knight is fully playable, too.
8. Strategy Supersedes Tactics
A player with good strategy but dodgy tactical vision can be helped, both during individual games and over time. They're at least on a constructive path. Players who go on strange adventures are often completely un-carry-able. They don't ask how they got misdirected, and why they get impossible positions.
Tactical trip-ups are understandable. Bughouse is fast paced. But tactical mistakes in service of good strategy are very often salvageable. Even costly mouseslips don't ruin games as much as the strategic silliness of sac-sitting.
9. Exceptions
With high flow from the partner, aggression is not only possible, but necessary. Steinitz's rule that the side with the advantage must attack or lose their advantage seems to apply just as much in bughouse as it does in standard chess. In certain games, development has to be balanced against board presence. Using the droppers. But these exceptions are quite rare below a certain level.
10. Conclusion
I have an older blog post refuting arguments people sometimes give in favor of not developing. Hopefully this more constructive and specific post is more helpful. My suggestion is to try to implement the advice, and see how much more fun bughouse is when you see deeply and win consistently.
