For visualization to be effective there are a few things that should be done without fail. One, visualize at least twice a day, once right when you wake up in the morning but before you get out of bed. And again right before you fall asleep at night. These two times of the days are excellent times to visualize because your brain is in or very close to being in the alpha state which is term for a brain frequency state that is most excellent for making an impression on your sub-conscious mind. Impressions that we carry around with us in our sub-conscious minds tend to manifest themselves in our life whether they are positive or negative.
Before you begin your visualization practice the triangular or squared breathing technique for 7 to 10 rounds, then systematically tense and then relax your body beginning with your scalp/forehead then moving to your eyes, then your cheeks, neck, shoulders, upper arms, lower arms, hands, chest, abdomen, back, hips, upper legs, lower legs, and then feet. Tense these body parts one at a time by squeezing or flexing them for several seconds and then relax by releasing the tension/flexing and then feeling the residual effect of the tension while at the same time imagining that part of your body melting. The whole tense and relax process should take no more than 5 minutes.
Once you have completed that count backwards from 50 to 1 visualizing the numbers as you go. If you find yourself getting lost in thought somewhere along the way then start over at 50 again. This exercise will help you to build your power of concentration; you want to be able to be able to count from 50 to 1 without loosing your count or loosing yourself in thought.