Lighting for older or larger people... that's a bit of an open ended question. For example if you look at pictures of somebody like Morgan Freeman they are often lit to emphasise his facial features as he has a sort of "elder statesman" mystique about him. I am going to assume however that you are looking for flattering lighting options. The key to working with anyone is about assessing how shadows work for them. If the lighting is too hard you will emphasise any unflattering shapes, too soft and you can make them look shapeless. Be careful with chin shadows in particular. Posing is equally important in this respect too. I do have to disagree with a couple of the other posts, there's no simple "this angle works best" approach. Working with any model of any size requires a certain level of analysis about their proportions, figuratively and facially to work out what works best for them.
The most important factor here though is not about what lighting, lens, angle etc. to use, it is about your rapport with the subject. I'm a still life photographer these days but spent a couple of years working in a studio that did a lot of portraiture. Making sure the subject feels comfortable and confident will gain far better results than perfect lighting and all of the best kit in the world ever could!
