I’m now going to suggest some rules to you, which are good general rules of thumb, but which you shouldn’t follow like a lemming. You can – and probably should – break all of these rules if you have a reason to do so. But following them will give you a good writing workout and will generally help you write effective, muscular prose.
Also, don’t think too much about these rules when you write your first draft. First drafts are for spewing text onto paper as quickly as possible. Use the rules to refine your text, later, while editing and redrafting.
[Can you start a paragraph with ‘however’?] (https://www.quora.com/Can-you-start-a-paragraph-with-however/answer/Marcus-Geduld)