Yep, Blueditch42 has fairly much covered it. Some people will tell you differently. Two basic schools of training; conditioning when it's still very young then break faults later and the other school, train them when aleast a year old, no bird or gun introduction until then. The latter feels that better to not let bad habits form.

I personally like the first school. Let the puppy on birds when the puppy is ready for it. At around four months, puppys from good hunting lines will show an uncanny interest in anything that flies. So, you start feeding birds and they'll be bird crazy for life. It doesn't have to be planted birds, just take the pup out as they'll start pointing skylarks. What you're doing is conditioning (no pressure) them for birds for whenactual training (pressure) starts.

Neither school is bad as I can surely understand both. It would be much easier to train in the latter and no worry about getting birds but I feel that you are missing a golden opportunity to build that drive. I personally don't know which is better for field trials or hunting as I entered a field trail once in my life.