How to wear a toga made from a bedsheet
You're going to a toga party with nothing to wear!
Toga parties are a college tradition dating back over a century. Dressing up like an ancient roman or ancient greek and acting out scenes from Caligula are as much a college tradition as calculus-based physics and microeconomic theory. If you're going to attend a toga party, it's important to do it right, or at least half-ass it in a way that looks reasonable.
The traditional toga was a very long garment, usually about 15 feet in length, and about 6 feet wide. It was draped over a shoulder and then wound around the body upward and fastened with a brooch that was called a fibula. Despite what you see in movies, it was not traditional to not wear anything under the toga. They generally wore a tunic-like piece of clothing for additional covering under the toga.
One thing to consider when preparing for a toga party is your footwear. The ancients didn't have sneakers, so your most authentic-looking choice is probably going to be a pair of leather sandals. I'm sure someone out there has written a detail thesis on ancient footwear and how to replicate it, but that's just trying too hard if you ask me.
Using a bedsheet as a toga
Find an unstained bedsheet that's either white or near-white in color. It's important that this is the top sheet and not a fitted bedsheet. You don't want to be walking around all night in a toga that's got elastic everywhere.
This method for wearing a bedsheet toga that I'm about to tell you is in no way authentic to the original, but who cares? You're wearing a freakin' bedsheet to a party! First, fold the bedsheet once lengthwise. Wrap it one and half times around your waist. Pin it. Throw it over your shoulder and bring it back down to your waist. Tuck it in to the part that's wrapped around the waist and pin it again.
A more authentic toga
If you really want to go all out, you can buy a 18' by 5' section of fabric. You probably want to go with muslin, cotton, or poplin fabric. The popular way to tie it was to drape it over the left shoulder so it would hang all the way down to the feet. The remaining fabric was wrapped around the waist and then back up and over the left shoulder, leaving any excess material hanging behind. A metal fibula, or brooch, pinned the toga in place just below the shoulder.