If you wish to get the most from a phone consultation with your vet, you will have to be organized, brief, and attentive. So make sure you jot down some notes before you pick up the phone, and keep pencil and paper handy to make notes. It's silly to make the call, then not remember what the vet told you to do, or to remember that there was another important detail you forgot to mention before you hung up. So get organized first! Make those notes: Easiest is to make one-sentence bullets of what you want to cover. Then leave space for the answers and information you wanted from your vet.
Before you call your vet, collect all the information you can so you don't waste time going back and forth to your horse's stall while your vet waits on the telephone. Try to decide if you need the vet to come—either right away or later, when it's convenient for him, or if you just want advice. Ask him for his opinion, if you're unsure.
If the problem is an old problem, one for which you've already consulted with your vet, do you just want to update him or her, or do you want to see if the progress your horse is making is appropriate? Try to have the information available so your vet can give you informed advice:
First, refresh his memory on what the original symptoms were, and what treatments you've administered.
Tell him what progress the horse has made. For example, his temperature is lower than originally or normal, but he still seems not up to snuff. Or he's still somewhat lame, but seems better than when the injury first happened. Or the wound is healing, but not yet healed, or showing signs of redness or swelling that seems not right to you.
Be concise, and be ready to tell the vet if you want him to come see the horse for himself, and if so, do you want him to come that day or right now, or can it wait until he can fit a visit into his schedule. Or tell him that you just wanted to report on progress, and ask if that progress is what he would have expected.