When people request an invite, I go to their profile to see when their account was created and how much they’ve posted.
If they created the account that day and all they’ve posted is that one post asking for an invite, nope, sorry.
The way I see it, the people who deserve invites are the ones who have stuck around here and contributed to some degree to the conversations.
I do it based on how polite they are. I only posted like once before I got an invite and I’ve stuck around.