Most toilet seats are held in place by two plastic bolts that are generally no more than hand tight.
They can be easily loosened with a flat blade screwdriver or even a butter knife. Chances are the nuts are loose already.
Just loosening the nuts will cause a seat to slide around a bit. Remove the nuts altogether and the seat will slide all around the porcelain and will only be held in place by those plastic bolts.
If you remove the bolts, it's almost too uncomfortable to use the toilet!