I just had my third colonoscopy and have a few tips and some info for you, based on my experiences with the test.
The prep day (day of fasting before the colonoscopy) is a lot easier and much less boring if you provide yourself a variety of liquids to choose from. My doctor allowed Ensure, Boost and Glucerna along with the clear liquids so I chose Butter Pecan Boost to drink for breakfast, lunch and dinner. I also made Lime Jello so that I could still have something to "eat" during the day (be sure to stay away from anything containing red or orange food coloring). In addition to water, I drank tea, chicken broth, clear Powerade, Sprite and white grape juice.
One of the nurses suggested that I drink at least 2 quarts of fluids throughout the day, which I did, starting when I woke up and continued every 30 minutes. I set a kitchen timer and drink at least 4 ounces every 30 minutes until it was time to drink the jug of HalfLytely, the prep solution. It's also important to drink plenty of fluids after you complete the prep solution. By doing so, I avoided the sometimes painful cramping that comes on during the purge process. I wish someone had told me about this before my previous colonoscopies.
If you're drinking the liquid prep solution, drinking it ice-cold and through a straw makes it go down a bit easier I find.
Another tip is to have the softest toilet paper you can find and/or some flushable personal hygiene wipes for when the prep solution and Dulcolax pills kick in. Using Vaseline as a coating during that time helps a lot too.
By far, prep day is the unpleasant side of the whole experience but, as mentioned, drinking a lot during the day really helps.
As for the procedure itself, you won't feel or remember a thing. The nurse starts an IV, then you're fitted with several monitors (blood pressure, etc.), the doctor comes in and talks with you for a bit and before you know it, you're out! You'll wake up in recovery and then someone drives you home. (I was even given a biscuit and soft drink to eat when I woke up and was fully responsive.)
The day of the procedure you are to take it easy...do nothing but rest. You'll most likely feel a bit bloated and gassy...same for the next day, though not as much. Other than that, you feel fine...very little, if any, discomfort.
I hope this helps some and that all goes well for you. Take care.