Question

What would be the best technique to separate a soluble solid from a solution, like separating salt from a mixture of salt water?

Answer 1

The best way is by heating the solution. The liquid will evaporate leaving the solid, such as salt, behind. 

Answer 2

The best method is to let the water evaporate, unless one wants to recover the water. However, case one would distill the mixture. So the water is still distilled and separated in a different container, as the solid salt remains behind in the distilling flask.