Most elite athletes use a 2-2 breathing rhythm. That is, they breathe in for two steps and they breathe out for two steps. The 2-2 breathing rhythm means you are taking 45 breaths (assume you now have a strike rate of 90) which is slow enough to allow for good depth of breathing. It is recommended to practice all kinds of breathing patterns, just to become familiar with them and to note your body's reaction.
Try the 3-3 breathing rhythm, 4-4 breathing rhythm and unequal breathing rhythms such as 3-2 and 2-3. Most athletes (except sprinters) use either a 2-2 or a 3-3 breathing rhythm. I suggest using the 2-2 breathing rhythm starting the breathing cycle on the left foot. If you use the 2-2 breathing rhythm and you experience a stitch, then switch the breathing rhythm to start on the other foot or switch to a 3-3 breathing rhythm until the stitch subsides.
Long term analysis conducted by Jack Daniels has found that elite athletes in races up to and including the 10K use the 2-2 breathing rhythm at the start of the race and after completing about two-thirds of the race they switch to a 2-1 breathing rhythm. For races longer than 10k the 2-2 breathing rhythm is used for the whole distance, perhaps shifting to a 2-1 breathing rhythm in the last minute or two for the sprint finish. An important point is that your breathing rhythm will not only tell you how hard you are working but also allow you to control how hard you work.