Well, first - there are several ways that you can directly read the text from a textbox on a different form, depending on what you want to do.
If it is accessing a parent form from a child form, the parent form will need to be instantiated. Then you just have to create a public textbox object and then set your textbox equal to this. You can then access all of that textboxes methods and properties.
Another way would be to create a constructor in your child form that allows you to pass in the form that you want to access. This will let you access all of that forms methods and properties, assuming that they are of the correct scope.
If it is a child form that you want to access, you can simply access the text properties of the particular textbox when you instantiate the form using something like: frm.TextBox1.Text where frm is current instance of your child form.
However, if it is settings that you want to use in your application, there are a couple of ways of doing this.
You can either read/write these to the registry, a database, an xml file, a text file, etc. If you did this, you wouldn't have to worry about passing these variables among forms. There is probably no best choice for these, all have certain benefits so just choose the best solution for you.