How do you say too in Japanese?

The particle used is も (mo), which also works for adding emphasis on certain Words.

e.g. あなたも・・・ [anata mo] = you too

私もそう思います [watashi mo sou omoimasu] = I think so (or I agree)

If you are looking for a phrase like "in addition to..", you might use ～の外にも [no hoka nimo].

e.g. 小学校１年生は読み書きの外にも数学も学べます。[shougakkou ichinensei WA yomikaki no hoka nimo kagaku mo manabemasu] = First grade students in elementary school are able to study math in addition to reading and writing.