I think you should not worry about undisposed objects. That is the GarbageCollector's job. If an object has no references to it then the garbage colector automatically disposes it.
But if you just want to call the dispose method, whenever you use an IDisposable object, suround it with the using keyword:
private void DoDadaBoom(){
using(var bitmap = new bitmap(params))
{
DoStuff(bitmap);
dode = new bitmap.clone();
}
}
The using keyword disposes the object at the end of the using block.