For the most part, most modern Fords are ok to jack on the sills- however, whereas in a garage with e.g 2 post ramps and rubber covered pads on the contact points of the lifting arms this is fine, I would not use axle stands directly on the sills as the contact area is quite small (and it's metal on metal) meaning damage could occur. Using a trolley jack on the sills is ok if it's got a rubber pad on the saddle, or I use a block of wood if not.
Unlike Ford however, I discovered the hard way in my early days that VW's (and by the same token the Mk1/2 Galaxies as they are basically VW designs) are not designed to be jacked on the sills, they are not load bearing and will crush if you do jack them there!
What I tend to do usually is use a trolley jack and block of wood on one of the box sections under the vehicle (or sill if suitable/ appropriate) and then once the trolley jack has lifted the vehicle up then position an axle stand under e.g one of the main front or rear subframe mounting bolts as Chris/ johnnyroper has said or other suitably strong load bearing area. Of course, some vehicles have dedicated jacking points fitted.
