How to know when the time is right...
When you can drive our Barrow over the lawn, without leaving a trace, then you know that the lawn has dried up after the winter and it has become time to clean.
Also take the opportunity to fertilize the lawn if rain is expected, preferably with chicken manure, which gives good powder to winter-tired grass.
If your lawn has bare spots, you simply roughen the soil with the rake and sow new grass. When done, start the grill and find a comfortable place in the sun.