That all depends on your expectations and comfort levels
What are plans/ideas ?
Are you out for a couple hours, day, days ?
What type of environment, hot, cold, wet, dry ?
At the VERY minimum, beer.
More questions than answers
Using the online mining guide, figure out where to go
What type of mining to do, for how long, using what type of equipment will dictate what you may want to bring along
Get out there and find the fever.