What are some strategies a business could use to learn about the local competition?

The previous
answer has some good ideas for finding out about the identity and location of potential local
competitors.  However, it is important to realize that it is not enough to know who your
competitors are and where they are located.  

Typically, when someone is
creating a business plan, they need to include a section on the competition.  They need to have
as much detail as they can on the competition.  They need to be able to, for example, describe
how the competitors' products compare with the products they hope to sell.  They need to
understand how much the competitors are achieving in the way of sales.  In other words, they
need to know much more than where the competition is located.

Of course, all
of this can be exceedingly difficult to obtain.  One thing to do is to actually go to the
competitors' places of...