Great thread.
I'm 53. I made my decision last winter to commit to fitness. On Jan. 5 I weighed 257 lbs. I went on a freaky diet, the HCG (Human chorionic gonadotropin - intramuscular injections) program and today I weigh 207 where I am holding steady and/or losing slowly, but it's hard to tell because I'm gaining muscle mass. I was running 3 miles every other day, but I have a huge health insurance deductible and my doctor pointed out to me all the great things I could buy for the price of a single bad knee, so I am now I am hiking 3 to 5 miles every other day on the Methow Wildlife Area, gradually increasing the length and steepness of my hikes.
I also lift weights every other day. Dumbbells mostly, 3 sets of progressively high reps, focusing on my shoulder (both major and minor) and back muscles. And various core exercises, like elevated push-ups.
My main concern now is injury, but I think I'm on the right track. I just got a book on shoulder injuries from the library that has a bunch of good stretches to try.