Frequent low-level movement is easily the most important type of exercise. This can be as simple as getting up for a quick stretch or walk around your office or house every 20-30 minutes (bonus: these quick breaks also help to improve productivity).
The easiest way to incorporate more movement is with three 5-15 minute walks per day. For added benefits, you can schedule these walks following meals, as post-prandial (after eating) movement can help to reduce spikes in blood sugar.
Longer walks after dinner are also one of my favorite ways to unwind and get ready for a relaxed evening.
Weekly goal: Aim for 5-6 hours of low-level aerobic activity this week.