Step back and decide how much to trim. This is important because it is not unusual for first time juniper trimmers to trim more than they want. You can always trim a bit more later. Don't trim more than 25 percent of the bush at a time.
Use hedge trimmers on newer growth and loppers on older, tougher growth. If you are trimming the junipers back and removing new growth, simply trim off the light green shoots. Make cuts with the lopper at a 45-degree angle and make the cuts as clean and neat as possible.
Don't cut beyond the last green growth on a limb. Beyond this point the limb may not recover.