there is no difference between,both words mean 'how'.
but “怎么样” can be used in negative sentences , instead of the action or situation you can not say it directly , it is a euphemism
for example,His article is not very good.（他写的文章不怎么样）
in this situation ,we often not use "怎样" in our written language.
In some degree,you can say 怎么样 is more euphemistic than 怎样.
and 如何, it means
1.how ( in what manner or way; by what means )
eg:How does this machine work?这台机器是如何（怎么、怎样、怎么样 any of them is ok) 工作的？
2.in what state or condition.
1. how( for what reason or purpose; why.)
eg:How is it that he left early? 他怎么离开得怎么早
eg:He did not like you very much. 他不怎么喜欢你
3.however( we often use “无论”、“不管” and other words in front of 怎么，and put “都”、“也”ect. behind.)
eg:He is very tired,and his mother asked him for sleeping many times, however he ...
4.used in a rhetorical question or exclamatory sentence, express affirmative, negative , or emphasis
eg:怎么，你没认出我？Whaat, you did't recognize me?
yes,as naomi said,啥 is a dialect in the northeast of China.
and as you know it just means what~
you can just change the “什么” in the sentence into “啥” ，that''s ok.
for example:你什么意思 ？（ What do you mean）