Wait until late in the winter season to trim your douglas firs. Try not the prune the trees later than the early spring.
Use long lopping shears to prune the edges of your douglas firs. These will allow you to reach higher areas more safely.
Prune lower branches on your douglas firs so that the amount of trunk left exposed on the bottom is the same for each. Use a tape measure as you prune to check your work and ensure you get each tree to match the rest.
Strip smaller branches from the base of the trunk for a cleaner appearance on each tree.
Take off the tips of small branches all the way around each douglas fir so that each one ends up with the same relative circumference. This is one of the easiest types of pruning because you don't need to remove any large branches. Again, your tape measure can be helpful when matching the sizes of trees.