At LEAST 30 minutes before or after a meal. At least two hours before bedtimes, so it does not interfere with your sleep. KEEP WELL HYDRATED.
If you have a heart condition or any other cardiac problems, statistically you are better off waiting until the afternoon, since most "surprise" heart attacks occur in the early morning hours, especially immediately after waking. Start your pace off slow in the morning,
Avoid stimulants while exercising if you have any serious medical condition, especially cardiovascular problems.