What do people put in charoses and why?
Charoses is supposed to remind you of the mortar used for the bricks. One of the ingredients used is apples to remind us of the apple trees the woman gave birth under in Mitzrayim (Shir HaShirim 8:5). In Pesachim 116. and Tosafos there also mentions ginger and cinnamon to represent the straw and clay used in Mitzrayim.
R'Gershon Gold's good answer mentions some ingredients, with reasons. Another is egozim (walnuts?) because of "el ginas egoz yaradti". I seem to recall also customs to include wine and dates, though I don't remember a reason for either.
Since the question seems to be asking what answerers do ("your"), I'll give you the ingredients of my family's charoses: apples, walnuts, cinnamon, ginger, wine.
I'll add to Gershon's answer, that Rav Schachter, following Rav Soloveitchik's lead, maintains that there should be citrus fruit in it, because based on the gemara which says it should be acidic like the tapuach, and Tosafot, in that gemara, it is not apples but rather citrus fruit. I discuss this, and its possible ramifications, here.