It depends on the weed and where it is. I also pour boiling water on weeds in paths and other hard paved areas but my brother once poured a kettleful on a dandelion in the middle of his lawn and managed to kill off more grass than weed..... idiot!
Dandelions in the lawn here get salt sprinkled directly into the middle, if they are in flower beds then they are dug up though their roots are so long it takes several goes to finally kill them off.
Most other weeds I just pull up as and when I spot them. I don't use any kind of chemical weedkiller as I have a cat and a small boy and worry about them ingesting it.