JavaScript instance functions versus prototype functions

Possible Duplicate:
Use of 'prototype' vs. 'this' in Javascript?

My understanding of the different kinds of JavaScript functions are as follows:

function MyObj() {
    this.propOne = true;
    this.publicInstanceFunc = function() {
        if (propOne)
            return 'public instance function';
    }
    function privateFunc() {
        return 'private function only visible inside this constructor';
    }
}

MyObj.prototype.protoFunc = function() {
    if (this.propOne)
        return 'prototype function shared amongst all instances of MyObj';
}

1. Are these correct?
2. In what cases should one put functions on the prototype (e.g. protoFunc) vs. in the constructor (e.g. publicInstanceFunc)?
3. Is using this the correct way to access properties inside prototype functions?