The standard tuning for a violin, is GDAE, where G is the lowest string and E is the highest.
How to tune a fiddle?
Often fiddlers use alternate tunings for fiddling especially for old time country fiddling.
Cross tuning is the most common alternate tuning - the most common cross tunning is AEAE, where A is the lowest string and E is the highest.
Another very common cross tunning for fiddling is GDGD, where G is the lowest string and D is the highest.
Another alternate tunings us for fiddling is DDAD called dead man's tuning - this tuning is often used for fiddling Hoedown.
I have a web page with more information about cross tunning and other alternate tunings.
For more information about fiddling using cross tunning, visit my How to Fiddle web page