When should I write Static Methods?

Question

So I understand what a static method or field is, I am just wondering when to use them. That is, when writing code what design lends itself to using static methods and field

Answer 1

You should use static methods whenever you have a function that does not depend on a particular object of that class.

There is no harm in adding the static keyword: it will not break any of the code that referred to it. So for example, the following code is valid whether or not you have the 'static' keyword:

class Foo
{
    public Foo(){}
    public static void bar(){}  // valid with or without 'static'
    public void nonStatic(){ bar(); }
}

...
Foo a = new Foo();
a.bar();

So you should add 'static' to whatever methods you can.