Honestly, or just looking and acting like you're supposed to be somewhere. It's surprising how many people just don't question you as long as you act like you're doing something you're supposed to be doing.
Ditch the clipboard for the kind of tools an electrician or HVAC tech would carry. Best to look like you're there to be helpful, not to snoop around and impose fines.
I've gotten into trade shows at Moscone for free by pushing a hand truck into the loading dock. If you look exasperated, people will get out of your way and point you in the right direction.
Depends on the exact circumstances and local trespassing and fraud laws. Ask a lawyer for details if you get a chance- perhaps reach out to LegalEagle, who makes Youtube videos about interesting laws and legal situations.
