There are three main type of calibration frames taken in AP.  They are Dark, Flat and Bias.  I will go over each one in detail on how I plan to create them.  The definitions below were obtained from astrobackyard.com.  An excellent resource for beginning AP.

Flat Frames – The idea is to evenly illuminate the field. The early morning sky is bright enough to create a successful flat frame, as long as you diffuse the light using a white t-shirt or similar translucent material. 

Bias Frames – The main reason amateur astrophotographers take bias frames is to reduce noise in their images, more specifically the fixed-pattern noise. No matter what type of camera you are taking your images with, the signal-to-noise ratio (S/N) is often the primary deciding factor between a good image and a great one.

Dark Frames – Essentially, applying dark frames to your final astrophotography image will reduce the amount of noise in your image. You will benefit from an improved signal-to-noise ratio, which means a higher quality image with lots of detail.

I started working with flats by taking a couple of test images.  I pointed my scope straight up and used my tablet by turning the display all the way down and set the background to white.  I took a couple of sheets of 20lb printer paper between the scope and tablet and fired off a couple of shots.  I compared the histogram in Adobe to what the astrobackyard.com example said was good and they looked to be really close to the same.