pull out a box of psuedephed (the real stuff) if they practically fall over themselves trying to grab it they are an addict or run a meth lab.. usually though if they run a lab they use too.

oh and the usualA meth user may exhibit some or all of the following symptoms and behaviors and may have some or all of the listed paraphernalia:Physical Symptoms:* Weight loss* Abnormal sweating* Shortness of breath* Nasal problems or nosebleeds* Sores that do not heal* Dilated pupils* Burns on lips or fingers* Track marks on armsBehavioral Symptoms:* Withdrawal from family and friends* Change in friends* Disinterest in previously enjoyed activities* Increased activity* Long periods of sleeplessness (24-120 hours)* Long periods of sleep (24-48 hours)* Incessant talking* Irritability* Twitching and shaking* Itching* Decreased appetite* Erratic attention span* Repetitious behavior, such as picking at skin, pulling out hair, compulsively cleaning, grooming or disassembling and assembling objects * Aggression or violent behavior* False sense of confidence and power* Convulsions* Carelessness about appearance* Deceit or secretivenessParaphernalia:* Rolled up paper money or short straws* Pieces of glass/mirrors* Razor blades* Burned spoons* Surgical tubing* Syringes/needles