Halter training is a very important first step to all training with llamas. Although each llama's reaction to the halter is different, it is really just about getting a halter on them and waiting out their tantrums until they finally accept it. A great way to get an older llama to like the halter more quickly is to only give them grain when they are on halter. Once they have gotten used to the halter you can begin to ask them to walk. I give a lot of treats in the beginning when a llama follows me, slowly weaning them out until they are not needed any more.
Tip: A good halter behaviour tip to save grief in the future is to never let your llama graze grass while on halter. This stops them from constantly trying to graze rather than focusing on you during training