Always start your workout:
Stretching to prevent muscle cramping leading to strains
With a good nights sleep and a healthy meal the night before
Starting slow and working your way up
After all, Rome was not built in 1 day and neither is the body you have had for many years! Be patient with your body as it goes through the transformation. It may take days to weeks to start seeing change. Sometimes the initial weight loss is water weight so avoid focusing on the scale and focus on the body changes through the clothes you wear. Commit a month to your exercise routine before expecting some changes.