Take a look:
|Warning! Comma missing!|
So, what are the rules for punctuating "however"?
When it's a conjunctive adverb joining two sentences, it needs a semi-colon before and a comma after:
The food was terrible; however, we at it anyway.
When it's an aside or interruption in the middle of a sentence it needs a comma before and another comma after:
The food was terrible, however, but we ate it anyway.
Addendum to Rule 2:
If however is used as an aside at the end of a sentence (see the closing sentence of this post, for example), then it should be introduced - set apart - by a comma.
When it's an adverb meaning "no matter how" it doesn't require any punctuation.
However you look at it, the food was terrible.
Writers and editors need to learn just three simple rules. I'm sorry to say, these rules are frequently broken, however.
(Sorry! Couldn't help myself...!)