I recommend putting a well-fitted leather halter or foal slip on your new foal within a couple of days of birth, so that wearing it becomes a normal part of his life. If you take it off and put it back on regularly (a good opportunity to check that it still fits him!), he'll accept that handling as part of his routine.
Here's how to go about this simple but important procedure of haltering with the best chance of calm and success.
1. I start the haltering process with my body close to the foal's and a little behind his left shoulder, because his first reaction will be to back away.
My right arm is over his neck, letting my hand guide the halter onto his nose. That same hand can also drop down beside his neck and anchor him if he steps away from me. If he makes a really sudden move, though, I'm positioned to give up on the halter and step out of the way without getting hurt--then try again as soon as he calms.
We're out in the field because this foal has been haltered many times and accepts it calmly; if he were new to the process, I'd begin haltering with him and his mother in a stall, a small paddock, or some other enclosed area.
2. The halter slips on easily, and I'll need only a few seconds more to do up the buckle--but if he starts to wander off, I'll walk with him (the halter over his nose already gives me a little extra control). I'd rather work with a moving target than risk upsetting him by trying to make him hold still while I finish.
For more young-horse-handling tips from breeder and trainer Susan Sisco, see her story "5 Must-Have Weanling Skills" in the January 2006 issue of Practical Horseman magazine.