I'm always wanting to learn and I don't feel qualified to actually share tips, but here were a few things I wish I had known earlier:

• when my mascara was drying out, I went too long before learning I could spray a little sterile saline on the brush (shaking off any excess drips of saline), and put the brush back into the bottle and work the brush a bit - then it would apply to the lashes perfectly without clumps (I've enjoyed mascaras like Mineral Fusion and Better Than Sex).
• lash curlers are a life changer, I have long lashes but they're heavy and droop down, and I thought it was a mistake with how I was applying the mascara (and the mascara weighed them down even more!!); maybe this is just obvious, but I went too long without using one and they really lift my eyes, even just the curler without the mascara is a big help
• foundation can really age you, so it's important to prioritize skin care and "natural beauty". It really sucks when my skin is breaking out and I have to cover up with foundation because it ruins the natural, soft look of my skin; I wash my face every night with a cleanser (occasionally using a more exfoliating salicylic acid cleanser on my nose) and use a night cream with ceramides. Hydrating throughout the day is also important to healthy skin. (As is diet, tbh.)
• I had no idea that cosmetic sunscreens existed, I wish I had known there were sunscreens that didn't feel like covering my face in grease, I've gone without sunscreen for decades because I had no idea. Discovering Japanese and South Korean sunscreens that function as a makeup primer, and aren't greasy and absorb into the skin, completely blew my mind and made it so much easier for me to put sunscreen on every day. I have really enjoyed CANMAKE's Mermaid Skin Gel and SKIN1004's Madagascar Centella sunscreens in particular.

What beauty and makeup tips did you wish you knew earlier?