Punctuate for meaning. For example:
A woman, without her man, is nothing.
A woman: without her, man is nothing.
The rule of thumb with commas is "less is more". Only use them to clarify meaning or to give the reader breaks by demarcating adverbs, subordinate clauses, and any other words or phrases that will help the reader navigate her/his way through the text with ease.
Given examples  through  below, you could either add a comma or leave it out. The meaning won't change with or without the comma. (Keep in mind, though, that some readers will expect to see a comma because they've seen it there before in other writings).
 I will wait a little longer yet.
 He went to the tanning salon and then to the gym.
 I would like to go however.
 He went to the bakery too.
 I would not go otherwise.
Add a comma in example  only if you want to show that Jason wrote the sentence:
 Come with me Jason.
 Come with me, Jason.
Example  is ambiguous. It could mean "Jason, come with me" or "Come with me, [signed] Jason", wherein the comma could mean 'said by' (Jason). Writers try to reduce the ambiguity by either putting the name first, like this, Jason, [you need to] come with me OR by leaving the comma out, Come with me Jason , which means the same as Jason, come with me.
Here are the answers to the questions you emailed me:
Ex: Thanks in advance and, also, for all your help last night.
Ex: By the way, should ...Again, you needn't use commas as I have above, but readers do in fact expect them, and plus it's a good rule of thumb to know how to do something correctly first before deciding not to do it. In other words, learn how to use commas, and then learn how to leave them out.