If you are very worried, get a small sheet or a large but light (thin) towel. Corner the bird somewhere dark. Keep in mind you'll have birds flying everywhere, but if you move slow until you throw the sheet on the bird you want, it won't be too bad. Keep the eyes draped with the towel but leave some breathing space, especially if it is hot or you had to give a bit of a chase.
Other ways include sneaking up on them at night (You might get pecked, but usually not hard). If you are getting them off the perch, you can still use a towel, but try not to get birds jumping off the perch. If you are really good, dart your hands at their legs (in a dark area), get a firm but not hard hold, and in a smooth motion lift them upside down by both legs.