What’s the first thing you notice when you first meet someone?

i look at the whole package first and foremost... then if we have a conversation i tune in to the conversation and how they talk...can they string together a few good sentences. While we are talking i am taking my assessment of all the rest but in a classy manner... do they smile... what does their body language say... you know the normal :-)
The eyes are the key during this time cuz like you said... those are the windows but ya have to make sure they dont hypnotize you at times. hahah

Their way of talking.

I go for the teeth. If they’ve got 3 or less then it means they brew their own alcohol or they’re a parent to their siblings 😂

Eyes 👀

I agree, usally their eyes, but I mean if they're like 7'11 I'd probably notice how tall they were. So I guess it depends on the person.

Eyes and mouth. And feeling if they’re open to me.

I determine if they are the gender they project.

The eyes for sure or outfit

The smile

Eyes

Probably eyes and how they carry themselves

Whatever is visible in you it .

Smile or no smile.

Eyes and smile.

Voice and eyes.