I don't have a particular method, but I have found that using ties with really "slippery" silk makes it more difficult to get a good dimple. Ties that have thicker/firmer silk tend to get better dimples, particularly silk twill or madder silk.
I use a "double four-in-hand" knot, so I wrap the front blade of the tie around the tail twice before tucking the blade down through the loop and pulling it tight. I also give the bottom of the knot a light pinch just as I'm pulling it tight, so as to give the knot a nice "v" shape and I suppose that might help the top of the blade to dimple nicely.
The pinch is what is causing the dimple. The other trick is to make sure you tie is in a W shape as you do this. Ties tend to have a bit of "memory" so its somewhat important to try and get it right at the start of the tie's life . I'll explain more in person if someone reminds me.