One thing that is increasingly considered before anaesthesia is the risk of undetected Obstructive Sleep Apnoea (OSA). This is where someone has a tendency to pause or stop breathing during the night for significant periods (over 10 seconds repeatedly) and is associated with day time sleepiness. It is most common in people who are overweight, snore, and men with large collar sizes (17inches+)
If you feel this could be you then consider filling in this questionnaire and if positive bringing it to your doctor to discuss as early as possible
How much exercise can you do is an important factor in your ability to cope with the stresses involved in an operation. Many people during the wait for an operation are less able to take exercise (because of the condition requiring the surgery). However anything you can do to keep fit and work round any limitations is likely to improve how you manage during the operative period. For some this might be formal exercise but for others just practicing stairs or increasing walking distance around the shops etc. This can increase muscle strength and also improve your breathing and heart strength.