If you are a newcomer who has never drawn a realistic mountain range or if you belong to the perfectionnist kind who is always unsatisfied with the results, I have tried to give some practical suggestions in this tutorial.
Of course as the name indicates, the target is restricted to realistic maps.
If you don't care for realismus, you may freely disregard all and any suggestions I might give.
I hope it helps.
How to do realistic mountain ranges 1.pdf