That is very vague. Form1 and Form2 are instances of a particular class and therefore passing it to a static variable would mean that every instance of the class could use it. But if that's the case you simply declare a static variable and assign it to the class and not the class instance.
class Form2
{
public static string value;
}
...
Form2.value = Form1Object.SomeTextbox.Value;
Good luck!