How to Practice Vipassana? I have been practicing samatha for five years now and have rarely done any other kind of meditation. I have tried to practice vipassana in the past but get confused with how to do it.


First of all you place your attention on your abdomen,when i'm more used to my attention being on the tip of my nose. Is there a way to practice vipassana with your attention on the tip of your nose? I can avoid getting too concentrated with a technique I found by accident, by widening my focus to the entire nostril instead of just a point. This helps allow for thoughts, etc. to arise. Because I notice during samatha thoughts are minimum to none.
Please describe a method of practicing vipassana with the base/anchor being the tip of the nose not the abdomen.


Many thanks.
A hammer has two ends for a reason; one end is great for pounding nails, but not at taking them out. The nose is avoided in Vipassana for a reason; it is too apt to lead to calm.

That being said, it is of course technically possible to cultivate insight at the nose, if you insist. Vipassana takes as its base the four elements, earth, air, water, and fire. As per the Visuddhimagga:


  But one whose vehicle is pure insight, or that same aforesaid one whose vehicle
  is serenity, discerns the four elements in brief or in detail in one of the various ways given in the chapter on the definition of the four elements.
  
  -- Path of Purification XVIII.5


So, you have to find the elements at the nose; there is some faint pressure, which is the air element, and there is heat and cold, which is the fire element. The breath itself is a concept, so you can't use that as an object of Vipassana. You might note "hot, hot" or "cold, cold" or "hot, cold", as it presents itself. Also, "feeling, feeling" for the pressure. 

Having taken that as a base, you would then note whatever other experiences arose, based on the four foundations of mindfulness, as per the instruction given by a teacher.

And, what Anthony said :)