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I usually draw a diagram of the decreases and then check them off as I do them. It helps me keep track of where I should decrease and how many times.
Cast off the 7sts and continue with the row. You'll be working on one shoulder. Work the next row in whatever stitch you're doing until you get to 2sts from the neck edge, decrease. Turn, work back to 2sts from the raglan edge, decrease. Turn, work to the neck edge, dec, turn work back to the raglan edge and dec. You'll continuge this way, decreasing at every neck edge and every other raglan edge for the given number of times and until there are 3 sts left.
Whatever method you've used for the raglan decreases should be continued on the raglan edge. For the neck edge, you could work to 3sts from the edge, decrease and then work one stitch. That'll give you a neater edge if you have to pick up sts for a collar.