Graphs of sin x and cos x - easier transformations

How to sketch the graphs of 
 y = sin x
y = sin 3x
y = 1 + sin 3x
etc. 

Practice questions:

http://www.myimaths.com/tasks/library/alevel/lib/loadTask.asp?title=alevel/core2/trigIntro/Trigintro5TransformOH&taskID=2049