Where to look for a date depends on your circumstances and why you are interested in companionship. For example, if you only need a companion for a special event (a wedding, company party, family reunion, etc.), it may be possible to approach coworkers or casual friends with the invitation. If, on the other hand, you are interested in a more serious commitment, you will need to look for someone who can be more than a general friend.
The best places to look are locations that closely match your primary interests.
Just a tip: The best place I have ever found for meeting women was airports. I would think it was a stewardess and it usually turned out to be a pilot or other member of the flight crew. Just drinks or a meal together, but airports are the only pace I have never had a rejection. Following that, I just take a park.