It is also worth noting that you can pass through more than 1 parameter. id will be used to make up part of the URL and any others will be passed through as parameters after a ? in the url and will be UrlEncoded as default.
e.g.
return RedirectToAction("ACTION", "CONTROLLER", new {
id = 99, otherParam = "Something", anotherParam = "OtherStuff"
});
So the url would be:
/CONTROLLER/ACTION/99?otherParam=Something&anotherParam=OtherStuff
These can then be referenced by your controller:
public ActionResult ACTION(string id, string otherParam, string anotherParam) {
// Your code
}