Get-SPLogLevel
To create a new log file
New- SPLogFile
To set the ULS logging to Verbose
Set-SpLogLevel
-TraceSeverity Verbose
To set the ULS logging to VerboseEx - Verbose Extended Logs- This will captured SQL queries in the log.
Set-SpLogLevel
-TraceSeverity VerboseEx
To set Eventlog along with trace log(ULS)
Set-SpLogLevel -TraceSeverity Verbose -EventSeverity Verbose
To Clear the Log Level
Clear-SPLogLevel
To collect logs from all the servers based on Correlation
Merge-SPLogFile
-Path "C:\Logs\Log.log" -correlation <correlation id>
To collect logs from all the servers based on date & time
Merge-SPLogFile
-Path "C:\Logs\Log.log" -Overwrite -StartTime
"mm/dd/yyyy hh:mm" -EndTime "mm/dd/yyyy hh:mm"
For more options check https://technet.microsoft.com/en-us/library/ff607721(v=office.15).aspx