Stitch in time saves nine, the longer you wait for help the worse the consequences.
If you experience high fever, blood in waste matter or vomit, dehydration, nausea, extreme fatigue, or dizziness then get medical help.
I have found that increasing the liquids and reducing the diuretics (tea, coffee, most soft drinks can dehydrate you) combined with regular bran and/or fiber in my diet has helped me steer off blockages.
Processed foods don't play nice with me. Restaurants - esp the national chains - are notorious for using them and most of my triggers have followed a meal out. If I have to eat out, I avoid menu choices with too much cheese or fatty solids. When I shop groceries I consciously avoid processed foods and I cannot recall a trigger when I make my own meals.
If I feel a blockage coming on, I keep a stash of oat bran snack sticks that I take with lots of water, let it digest for an hour to work through the piping, then massage the area where I feel the blockage. The oat bran cleans the plumbing and massaging the blocked area can break something loose, I can feel it. Most times it works and my GI encouraged the practice when I told him about it. On the rare occasion it doesn't work, I head to the ER.