First Method: Using Central Administration

1) Open your Central Administration web page and Click “Operations”
2) Click Diagnostic Logging link

3) For enabling verbose mode for all categories:
Select and set “Select a Category” combobox value to “All”
Select and set “Least critical event to report to the event log” combobox value to “Warning”
Select and set “Least critical event to report to the trace log” combobox value to “Verbose”

4) Click OK.Its done.
Important!:Please don’t forget change mode to default after collecting needed verbose mode logging. Because in verbose mode log files grows rapidly and if you are not enough storage your sharepoint server would be crashed

Important!:Before enabling verbose mode ensure you have enough hdd space on ALL your servers. Because this is a farm configuration and all servers has been affected by this change.

For restoring default values.