You should only purchase costumes that are made of flame retardant material. If they are home made, make sure you use fabrics that are inherently flame resistant, such as nylon and polyester. The federal Flammable Fabrics Act (FFA) requires costumes sold at retail to be flame-resistant. To prevent costume-related burns, the U.S. Consumer Product Safety Commission (CPSC) enforces this requirement and recalls costumes and other products that violate the FFA act. If you are going to make a homemade costume.
 

Buy your costumes from a reputable online or brick-and-mortar store that sells high quality products and has efficient customer service such as the Costume Kingdom.

Try to work  reflector strips into your child's costume, a flash light or light stick to make them more visible at night. This will make them more visible by drivers and you can keep an eye on them as well if they get ahead of you while out trick or treating.

Make sure that your costume fits properly to avoid any accidents like tripping over a long dress or cape. Make sure that it is comfortable since it will probably be worn for several hours. Do not include high heel shoes or long dangling pieces of costume that could be tripped over. A scraped knee or bloody nose can really ruin the fun.

If they are carrying a prop such as a scythe or sword, make sure they are made out of a flexible plastic that will bend if fallen on. Most of the props available today are made of flexible plastic.
 

Be sure to pre-test any makeup you plan to use by applying a small amount on the arm of the person who will be wearing it for about thirty minutes a couple of days in advance. If a rash, redness, swelling, or any other signs of irritation develop where the makeup was applied, it could be a sign of a possible allergy or adverse reaction.
 

If a mask is worn, make sure that the eye holes are big enough to see not only in front but peripherally as well. You may have to cut them open further yourself. If so, use some black or gray grease paint around the eye socket to cover skin.

If going out with a group, choose or make the costume a unique one, so it can be spotted easily in a crowded area. Use flashing lights or jewelry to stand out.

If you have more than one child, save costumes from year to year to pass down to younger children or exchange them with friends. You can add extra accessories or dress them up a little to make them different from year to year.
 

If you plan on doing any trick-or-treating with a group, and yes, some adults still do go out trick-or-treating, make sure that your group isn't too big and that you all have some type of reflective or flashing item on your person so cars can see if.
 

If you are wearing a mask, make sure that it is comfortable, has adequate eye holes and proper ventilation. If you have to cut the eye holes bigger, just use matching grease paint around your eyes to fill in where you have removed mask.
 

Women, if you are wearing something "low cut and sexy", as Elvira would say, make sure that you can easily get in and out of the costume for bathroom purposes. Nothing will ruin your fun at a night club or party faster than not being able to make it to the bathroom in time.