If you want to have the cops called on you, show up at your local park or ballfield with a full-sized shovel. You don't need a backhoe to plant a tulip, and you don't need a shovel to dig a coin. Many people when just starting out will stop by the home improvement store and get a gardening trowel. Others want something that will stand up to years of work and thousands of digs, and go for purpose-built “diggers.”
When choosing a hand shovel or trowel, look for a heavy duty one with a serrated edge, to easily cut through grass and small roots. Common garden implements that are popular include Fiskars Big Grip Garden Knife, Japanese gardening (hori-hori) knives, and the Wilcox 50S. Some of these can cost less than $10, but aren't as rugged as a purpose-built digger. Among “professional” digging tools, the Lesche digging tool, the Garrett Edge, and the Predator Raptor tools are popular.
We cover the proper way to use these tools in the “How To Dig A Proper Hole (Plug)” in the Beginner's Guide to Metal Detecting. If you haven't read it yet, be sure to. It's very important for the survival of metal detecting that people know how to recover targets without making a mess!