As a preposition:
* Do - used for motion, direction, or purpose. For example: "Idę do sklepu" (I'm going to the store).
* W - used for a location or time. For example: "Jestem w domu" (I'm at home) or "Spotkamy się w poniedziałek" (We'll meet on Monday).
* Na - used for a surface or purpose. For example: "Kładę książkę na stół" (I'm putting the book on the table) or "Idę na spacer" (I'm going for a walk).
As part of a verb:
* Aby - used to express purpose. For example: "Chcę iść do kina, aby obejrzeć film" (I want to go to the cinema to watch a movie).
* Do - used to express completion. For example: "Dojechałem do domu" (I arrived home).
It's important to consider the context to choose the right Polish word for "to".