MISSISSIPPI STATE -- While it looks great in a movie, real homes should never be decorated like the set of National Lampoon's Christmas Vacation.

Dr. Frances Graham, extension housing specialist at Mississippi State University, said there is one overriding safety issue concerning holiday decorations.

"Think before you act," Graham said.

Never place flammable materials such as curtains and Christmas trees near heat sources. Put lights on an automatic timer so they don't stay on too long.

"One of the biggest mistakes people make with their holiday decorations is leaving on lights decorating the house and the tree while they're gone or when they're asleep," Graham said.

When hanging outdoor lights, use only those labeled for outdoor use. Fasten the lights securely to trees, walls or other firm support to protect them from wind damage.

"Hang the outdoor lights with some type of rubberized hook so there is no way the electrical wires will rub against metal and be exposed and lead to a fire," Graham said.

Use only UL safety listed lights and decorations. Never use more than the recommended number of lights on each circuit.

People often create a hazard when decorating homes for the holidays by overusing electrical extension cords.

"Holiday decorators depend on extension cords to use several electrical appliances and decorations," Graham said. "But these can be easily overloaded when you plug in multiple units."

Try to eliminate extension cords and plug directly into wall outlets. When using extension cords, check labels to make sure the cord's rating matches the appliance's rating. Follow the directions on boxes when plugging strings of Christmas lights together.

A beautiful part of many holiday season decorations are Christmas trees and greenery in the house. These pose their own safety concerns.

"When picking out a Christmas tree, choose a fresh-cut tree as it will stay green longer and be less of a fire hazard than a dry tree," Graham said. "Fresh trees should be deep green, have a strong scent of pine and the trunk should be sticky with sap."

Don't rely on chemical coatings to make a live evergreen flame- resistant. Be sure the tree is out of the traffic pattern and doesn't block doors. Also, keep trees and greenery away from fireplaces, radiators and other heat sources.

"Trees left near heaters and fireplaces dry out much quicker, making a volatile situation in homes," Graham said. "Trees can become flammable when you least expect it, and heat -- not just fire -- can ignite them."