First, take calves, not grown cattle. They are easier to handle and cuter. They still smell though, so wear old cloths. Timing is everything. They should be weaned and eating grass. You don't want to bottle feed a bunch of calves. Trust me. Find a pasture with a side road so you are out of sight more than on the main gravel road. Never rustle cattle from a highway. The fence should be strands of barbed wire, not that grid stuff. You need an accomplice. Your accomplice stays outside the fence, you go in. The wire is slackest nearest the center of a section between two fence posts. Find a spot where there are not cowpies inside the fence. Lay down along the outside of the fence, right next to the wire, facing up. Lift the wire as high as you can above you and scootch sideways under it. You are in. Leave the calves with unique markings in favor of the bland average ones. Get between a calf and its mother to separate it. Wave your arms to scare the mother away. Grab the calf around its legs and take it to the fence where your accomplice waits. Hold it over the fence and have your accomplice put their arms under its belly so you can roll its legs up and over the fence int the arms of the other person. Your accomplice can carry it to the trailer and roll it down in. You can go back for more. Don't be greedy. A half dozen is a good start your first time. They will be more work to raise than you think. Don't become attached to them and don't name them.