How do I look out for good form + posture when doing strength training all on my own?

The way I imagine my hips, I have eight points. So it's roughly like a rectangle in my body with four points at the bottom and four on top. It's much easier to find the bottom, you can use the lotus pose to find your "sit bones" on the bottom (which is a painful, sometimes years long process to fully rest on your sit bones, but that's another thing altogether). Once you find your sit bones and can visualize them properly it's much easier to imagine keeping your hips parallel to the floor by using the visualization of your sit bones/bottom corners.

Idk if I can describe this right but lemme try.

When you're in the mountain pose, distribute your weight evenly. You should feel some action on the outside of your legs as you push your feet down into the floor at all four corners. Bend your knees ever so slightly (just make sure they're soft and unlocked). Tighten your buttocks, and the top part of your thighs near your groin. Keep your belly soft and push your hips forward slightly (us girls tend to stick our bottoms out so this will feel super awkward at first). Try to visualize your sternum and keep it perpendicular to the floor (we don't usually have any issues pushing our chests out and actually may need to bring it in a bit). This is the base of the mountain pose and if you're doing it right holding it for just 10 minutes (literally just standing) can be a serious workout. This should force you to level out your hips and square them properly. When you get the "stack" of all your joints in perfect alignment you will notice it. It feels a bit like you're settling into a groove, and you may even feel some joints in your spine pop as your weight finally settles evenly. But it does require you to keep tension on several opposing muscle groups so even as you experience that sinking sensation of falling into alignment it won't necessarily get easier to hold. If you relax the tension in any part of your legs/butt you're not really doing the mountain pose anymore. When you start out I'd recommend just letting your arms hang at your sides at rest because holding them up or out changes your focus and balance, just focus on your hips at first. There's a similar set of opposing muscle contractions for the chair/squats to help you keep your hips stacked properly but I'd have to look it up before trying to describe it.

Omg I haven't bench pressed in a long time. I do know that you're still supposed to line up your hands and shoulders still! One thing I experienced that I hope you never do is men/boys giving bad advice intentionally because they want you to fail or they're sadistic, so I'd highly recommend ignoring men or checking their work first before implementing any of their advice. It happens ALL THE TIME. I had boys try to trick me into breaking my own bones before (fortunately I knew enough to recognize that they were teaching me wrong, they always assumed I was a rank amateur), so please don't underestimate the malice of your male workout buddies.

Ahh okay! I have to ask, do we follow the same stacking method for all push ups, even knee push ups? Bcs I'm absolutely sucking at those and I've tried for over an hour....