The best way I've found is to use a C-clamp to clamp to the gear leg at some convenient height, padded by a piece of plywood on each side (a plywood/gearleg sandwich). The the jack hooks the head of the C-clamp and you jack it up. I've seen incarnations of this whereby a piece of steel is welded up at the proper angle with something sticking down for the jack to catch, is clamped in position the same way, and then jacked up. But the clamp and plywood blocks works like a charm. I use a floor jack, so tipping isn't a problem...
Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net