Don't even try to dig through solid icy dirt to plant garlic in the winter. If you miss the Fall planting season, there's always Spring. And visa versa.
Don't plant garlic in any area where water can easily collect around the roots, like a low spot in the yard. This can cause the roots to become diseased or to rot. Garlic does not do well in overly wet soil.
Don't plant any soft garlic cloves or ones with any nicks or punctures in them. The garlic head should be firm to the touch with no visible damp or brown spots.
Don't use garlic powder (much of the flavor is processed out) or garlic salt (contains large amounts of sodium ~ as much as 900 milligrams per teaspoon).
Don't use garlic to plant that has been wrapped in cellophane or store purchased garlic that you are unaware of the type you are planting.
Don't assume a small bulb produces only small cloves. While doing my clove separation activity, I discovered some of my tiny bulbs would still produce one huge clove alongside 6-8 tiny cloves.
Don't plant garlic purchased from a grocery store which has likely been sprayed with chemicals, pesticides and a hormone that prevents it from sprouting.
Don't overwater your garlic possibly causing it to become diseased or to rot if it becomes sodden during the cold months.
Don't plant garlic in clay-based soils.
Don't choose a mulch cover that attracts mice and other rodents to nest in your garlic.