So let's say you command a ship. You've paid your dues, earned your rank, and have knowledge of common-sense combat strategies and enemy ship-to-ship engagement maneuvers. I understand that shooting another vessel in motion at distances measured in kilometers (or more) with serious accuracy potential isn't all that feasible in this day and age, but you figure a few centuries from now you have weapons at your disposal which can perform tracking and self-correction in flight as well as targeting systems which are leaps and bounds more sophisticated than what we have today.

It follows that someone like Kirk can look at Sulu and say, "Target their port nacelle and fire at will." Mr. helmsman locks in the coordinates and presses the button. Phasers firing. Torpedo away. Hell, they were able to do this in a nebula when they had to shoot blind without sensors:

So how come ships in the 23rd and 24th centuries have obvious weak points in their hull design that could expose them to easy pickings? If I were commanding a ship that carried photon torpedoes and saw a Klingon threat in my way, this would seem to be a vulnerable area:

If the enemy is exposing his neck, why not take advantage of the situation? His loss, your gain. But let's switch chairs for a moment and take a look from the Klingons' perspective. If you're the type to get over-confident and cocky because you drive a cloaked ship that can fire at will but leaves smog trails which can be tracked by a torpedo with scientific cataloging equipment, you apparently aim for the most obvious part of the ship which is probably well-protected by design:

Wrong.

Listen - you're in battle. You want to win. You want to pass the word along to your peers that you defeated The Kirk. Don't savor the moment by playing games. A bunch of Klingons before you tried and failed, and just because you have an eye patch doesn't mean lady luck is on your side. Just shoot the damn bastard where it hurts:

Just pick one. Better yet, get above the Enterprise and shoot the bridge with everything you got. I guarantee you victory is on your side. If Kirk can do it against one of his own, so can you. And roughly a century from now, a Reman ship will do the same, but like an idiot her commander was over-confident too.

If you run a ship that big compared to your adversary and you have a boat-load more weapons, the word "failure" should not be in your vocabulary. At least Shinzon was smart of enough to clip a Romulan warbird's wing off and send it flying against the Enterprise, rattling her shields harder in the process. Two birds with one stone. Picard never did anything slick like this.

And then you have designs which stare down at you with an attitude. There may be support beams that you can shoot at, but none are directly exposed from the front. Besides, this Romulan warbird looks tough. I doubt Picard would ever want to head-butt with this guy.

However, those glowing green warp nacelles seem like an enticing target. Keep your weapons locked onto them and the instant they engage the cloak, press the fire button. Game over.

If you're the Borg, have already sent a boarding party to collect information, but still have a continuing insatiable curiosity about the ship to justify taking a slice out of the cake, don't hit up some random spot.

You're doing it wrong. See that little dome at the top of the saucer section that the ship schematics you downloaded probably refer to as a "command center of the entire ship?" Yeah, grab that instead. Your life may be a lot easier down the line. It's right there in front of you and well-exposed. It was made to be scooped up.

(And why is the color green consistently used by aggressor alien species? Romulans, Borg, Klingons, etc.. Pick something original.)

Let's turn our attention back to our old favorites, the Klingons. In "Generations," we witness yet again the Enterprise being torn apart because her shields apparently work on a single modulation frequency. Did Starfleet not remember the simple tactic of shifting frequencies after the Borg invasion? Shouldn't this be standard procedure by now? So after the initial torpedoes hit the Enterprise's secondary hull, Worf reports, "They have found a way to penetrate our shields!" Oh yeah, like no one's figured that out yet. Here's an award for stating the obvious.

A few moments later, Lursa and B'Etor decide to target the Enterprise bridge with full disrupters. Oh geez, here we go again... Shouldn't that have been the first thing they did? Now you've waited too long to put your real game face on and given the bright crew of the Enterprise time to figure out a way to sucker-punch you back. There's no honor in being stupid.

So the other ship has just farted a bright one and you have an incoming. Do you:

a) Apply emergency impulse and get out of the way?
b) Use your well-honed targeting skills and shoot it with your disrupters?
c) Stand there in shock, awed by your stupidity and hit panic mode with the "Crap, what do we do?!" expression?

Didn't we just see this in the previous movie? The scene was so poorly thought out that they brought back recycled footage from "The Undiscovered Country" to show the Bird of Prey blowing up. Here's a 50/50 of the same shot between the two movies:

If you want to play naive and claim that it's a remarkable coincidence that two Bird of Preys blowing up in two different centuries would have such exact same explosion characteristics and starfield pattern behind them, well ... knock yourself out.

The Duras sisters had an established history within the Trek universe. To have them go out like this is cheap. "Generations" was full of cheap moves, like Kirk dying the way he did.

Star Trek had too many instances where a single lucky shot saved the day. Again. In space, you're going to get into fights. Design your ships better or plate them with better armoring.