Saree Petticoats are, as the name suggests, worn under a saree. They are tied at the waist using a drawstring. The petticoat itself is flared broadly at the bottom.
The petticoat should be tied TIGHTLY at the waist - slightly above the upper elastic of your panties. In my experience, it is rather difficult to wear sarees if you are wearing high waisted tummy tucking panties. Your best bet would be to wear low waisted tummy tucking panties when wearing sarees.
Before you pull down the petticoat over your head - and yes you cannot step into a saree petticoat like you do for your trousers - pad up your hips by tying either a lungi or a bath towel around your waist. I have found that my regular bath towel is most effective to give the typical rounded look of Indian women. Strengthen the tying at the waist by using your male belt to hold it tightly in place.
Now pull down your saree petticoat over your head - obviously your hair should not have been done then. Tie it tightly around your waist. I keep emphasizing on the Tight tying of the saree petticoat for a simply reason - the petticoat is supposed to withstand the weight of your saree. So it is imperative that it does not slip down. Unfortunately, we males do not have the hips which can prevent the saree from slipping down.. so we have to simply bear the discomfort of a very tight Saree petticoat!
Selection of Saree petticoats
Color
A saree petticoat should more or less match the color of the saree you intend to wear. I find it quite hideous to see the lower hem of a Red petticoat under a blue saree! The color of the petticoat should not be so overwhelming that when viewed from outside, it spoils the look of the colors of the saree.
Let me explain: If you plan to wear a cyan or sky blue chiffon saree, then you should choose a sky blue petticoat or at least a white or a blue petticoat. If you choose a dark blue petticoat, then the saree's beauty will be marred.
If you take care of the selection of the petticoats, you will come across as a woman who takes care of the clothes she wears.
Length
The saree petticoat should end just at the ankle. Your best bet would be to measure the length from your waist to the ankle and specify it to the sales person.. (Obviously, you will look ridiculous if you were to hold the saree petticoat to your waist to ascertain whether the length is correct.)
Size
Ordinarily saree petticoats come in two sizes - one for a slim person and one for a fat person. Always choose the one for a fat person. As a closet crossdresser, I cannot possibly maintain slim legs to fit into a slim person's saree petticoat. Also remember the bath towel which has padded up your hips?
Designs
These days a variety of saree petticoats are available in the market. You get the routine workhorse kind of petticoats - totally unsexy and made of really thick material with just gathers at the bottom hems. You also get petticoats with lace at the bottom hems. You also get petticoats with zippers at the waist so that the slit to accomodate the broader hips of a woman does not result in a display of panties - or as in the case of a crossdresser a bathtowel!
Obviously, the more fancy the petticoat, the more expensive it will be. But if you plan to go out when dressed, you may want to determine whether the petticoat is transparent when in the sun. This will be a little difficult but you can always ask the sales person, explaining that on the previous occasion when you purchased a saree petticoat for your wife, she found it to be too transparent and inappropriate to be worn during day time.