Ask a friend or someone who knows you well. I started taking Concerta a few years ago and told a friend I was working with. I said "I took one this morning and I don't feel like it did shit".
He assured me that in fact I was a different person to work with, focused and detail oriented and not annoyingly chatty. ADHD meds should just quietly make your life better, not have a strong feel. Though the first time you take amphetamines or bump the dose you can expect to feel a little speedy I found. Good opportunity to clean your house.
One thing I noticed is that it feels like ADHD meds manipulate your luck. When you take them, things just go right. My wife informed me this is because I don't rush or make stupid oversights that feel like bad luck, but it really does feel like they are concentrated luck in pill form. If you feel like the bad luck and chaos that follows you around is gone, they're working.
Concerta helped me get my life together but I hated the side effects, thirst, flushing, exhaustion. I took Adderall XR for a year which was great, and then switched to pure dextroamphetamine XR because it was covered by my insurance and Adderall was not. It does the job without any side effects other than needing to drink a bit more water.