lift for at least an hour 4 times a week, doing one muscle group each time. eat a lot of fish, steaks, beer. do heavier weights but not something u can't rep at least 6 times. Don't forget to do back and legs. Don't bounce weights off ur chest, and do swinging body motions I think that will help avoid injury. Increase your weights maybe monthly once u get up to 170 lbs don't go up in lifting weight anymore. For tennis thats probably as big as you should be. I'm 5'10" also used to be 150 went up to 205 after lifting now down to 185-190 and I know my endurance would be a lot better at 175 ish. suffered neck and shoulder injuries trying to lift too heavy. yah number one don't injure yourself.