«Too» (usually at the end) «So» at the begining.
-«I´m in a hurry».
-So am I OR Me too OR I am too.
-«I need to go to the bathroom»
-So do I OR I do too OR Me too.
You can also use these expressions in the second or third person_
-She´s from Spain
-So is he OR He is too
-They´re travelling to Germany
-So are we/ We are too.
You can also express Agreement in negative way
-«I´m not hungry»
-Neither am I OR I´m not either OR Me neither.
-«I don´t want to go to eat tripe»
-Neither do I OR I don´t either OR Me neither.
-you can also use these in the second or third person.
-«Michael doesn´t like sardines»
-Neither does Samantha OR Samantha doesn´t either.
You can also disagree using shorter expressions:
-«I think Donald Trump would be a great president of the United States»
-I disagree OR I don´t think so.
Finally, you can disagree by stating the opposite opinión, sometimes stressing a Word for emphasis.
-«I don´t like vanilla ice cream»
-Well, I do.