Soap, hera markers which I think are soapstone, baby powder, cornstarch, etc. I even heard John Flynn suggest cinnamon one time on Simply Quilts.
I mark with a chalk pencil, just the area I will be working on for that row or spot. I've heard others who lay out their stencil and pounce the entire top then use hairspray--cheapest kind you can buy--to hold the chalk on. If you use the pouncing chalk, though, make sure it is the non-staining kind for quilters. Don't use the orange/blue/yellow chalk that carpenters & roofers use for snapping lines!
I've also traced onto very thin tissue type paper and used painters tape to hold it on the quilt and stitched right through the paper. That is my favorite method.
I'm afraid of the markers. Too many horror stories about them not coming out or coming out but resurfacing later.