Deciding whether a comma is needed before ‘too’ must be a nightmare. Contradictory explanations lurk on the web and critiques will often swing either way. There are a few rules that may help you decide what to do and the most important one is this: it honestly doesn't matter.
The Chicago Manuel of Style (note how it’s a ‘style’) has something to say here. If ‘too’ follows a change in the conversation, a comma may neaten up the parsing.
I saw the news. I saw my mother, too.
However, if you’re mentioning how you've done something the same as someone else, then it’s all part of the same conversation and topic and you don’t need a comma. Taking it out could increase pace.
You saw the news? I saw the news too!
However, general consensus now suggests these rules are optional. You can put the comma in and by doing so you’ll create extra emphasis.
You saw my mother? I saw my mother, too!
When ‘too’ appears in the middle of the sentence, you may find yourself wanting to put a commas either side of it to emphasise the point. This, too, is perfectly fine. If you find yourself wondering to comma or not to comma, then try both and see which sounds better to you. It’s mainly pace versus emphasis.
Keep in mind that commas are only there to make sentences easier to understand. It’s not a sentence-changing piece of grammar; use it as you please. If anything, it’s just style.