Is there any trick to hanging a screen door without it being crooked?

The problem with those thin aluminum kits is the metal flexes the second you apply any torque. When you drive that final screw, it’s likely pulling the frame into a void between the casing and the stud. If your shims aren't positioned directly behind the screw hole, the screw acts like a winch and bows the frame toward the house. That’s why your alignment disappears the moment you think you’re finished. You have to pack that space with enough shims so there is zero room for the metal to move inward.

First thing you shoud do is throw those kit screws in the garbage. They’re usually made of cheap zinc and the heads are soft as butter. Go to the hardware store and get some **#8 stainless steel screws** or even high-quality trim screws with a Torx head. They won't strip, and the star drive gives you way more control. Also, make sure your pre-drilled hole in the aluminum is slightly larger than the screw threads. You want the screw to pass trough the door frame and only 'bite' into the wood of the house.

And honestly, most door openings are rarely square. If you’re fighting the frame, check if your trim is the culprit. I’ve had jobs where I had to pull the 1x2 trim off completely becuase it was warped or installed poorly. If you install the door directly to the house framing and then put the trim back on *around* the door, you can hide the fact that the house is crooked while keeping the door perfectly functional. It’s way easier than trying to shim a door to match a crooked piece of decorative wood.

Don't tighten any of the screws all the way untill every single one is in. Close the door, check the reveal—that's the gap between the door and the frame—and then tighten them slowly. If you see the gap start to change as you turn the screwdriver, stop and add more shimming behind that specific screw. It's tedious, but it's the only way to stop that flimsy metal from shifting on you.

I’m about to start this exact same project next weekend and now I’m second-guessing everythign. I never even thougth about the screw pulling the frame in like a winch. If I switch to those Torx screws, is it safer to just hand-tighten them at the very end so I don't accidentally bow the metal?

Also, for a total newbie, what am I looking for when checking the "reveal"? Is there a specific gap size that’s standard, or do I just eyeball it untill it looks even? I’m terrified of stripping the wood in my door frame if I have to keep backing the screws out to adjust the shims.

Hand-tightening is definatly the way to go for those final adjustments. Using a drill for the last quarter-turn is how most people end up with a jammed door. As for the reveal, you're looking for a consistent gap—ussually about 1/8 to 3/16 of an inch—all the way around the top and sides. If it's wider at the top than the bottom, your frame is racking.

Pro tip: grab some wooden tongue depressors or even a stack of pennies to use as spacers. Stick them in the gap while you're setting your screws. It forces that reveal to stay even while you're fighting the frame. If the door closes and you can still pull the spacers out easily, you've nailed the alignment.