How to start with the weight training

Hi I have been on here since January of 2012 I am down 45lbs and am amazed at the energy I have. I am a 46 Yr. old female and just recently joined the gym. I have got the cardio down pat and enjoy using the strength training machines,,,My question is how should I attempt to start with some weight training? I have lots of sagging skin and feel like I would enjoy working with weights but really do not know where to begin since I have no personal trainer any ideas would be so much appreciated. Thanks I love this site it keeps me motivated.