just make sure your smoknig with friends that you trust and your in a place that your comfortable with. the worst high i had was when i was with my asshole of a friend whos against pot and we went to this trippy 50's style restaurant with neon lights everywhere and he kept saying that the cops were after me and that the watiress knew i was high, so i wouldnt look her in tha eyes and i was real scared n shit. but anyways, try taking a deep breath and telling yorself that its just tha weed making you paranoid.