I'm not going to sugarcoat it. Handstands, globally, are a bit of a disaster. This is a skill that is attractive to many and understood by few. If you search for tutorials online, I'm afraid to say you will find at least 90% incorrect instruction. Too many people think that catching balance while on your hands = handstand. Not so. As simple as a handstand looks, it is actually quite complex. Let's look at a few common mistakes:
Common mistake #1: Hands too wide
For a classic straight handstand, the hands should be positioned directly under the shoulders and arms squeezing toward each other. The placement is a lot closer than you think. When the hands are wider, you end up recruiting more lats and triceps, which can make it seem easier at first, but doesn't lend itself to a longer hold and does not represent a technical handstand. P.S. the handstand emoji's technique is on point!
Common mistake #2: Shoulders closed
If you hold your arms straight overhead, your shoulders are open. You may not be able to hold this position if your lats are too tight. As you bring your hands forward in front of you, your shoulders close. In a handstand, closing shoulders causes the torso to angle away from the shoulders rather than stack on top. That also leads to unwanted spinal extension (backbend). Again, closed shoulders can make the balance feel easier, but you won't have the line you're looking for and it requires more muscle, meaning you will fatigue faster.
Common mistake #3: Arching into your handstand
Entries to handstands are generally pretty messy out there in the world, but one especially common error is letting the back bend as you kick up. Instead, engage your lower abs and focus on maintaining that strength so you are either slightly hollow or neutral throughout your entry. Balance-correcting from an arched position is best avoided since it requires a large movement. Plus, uncontrolled motions around the low back can definitely cause pain.
I could go on--and I do in my How NOT to Handstand ebook. This ebook includes more than 20 videos with drills and demonstrations to help you achieve a technically correct straight handstand. Photos of correct and incorrect technique help you understand what to look for when assessing your own handstand. I also include a full handstand workout routine with a a follow-along video. Check it out!