for older nickels, steps can be a proxy for strike quality, but when during the 1980s the mint reduced the relief of nickels, full steps became the norm. so if you are looking to save recent nickels that will be in demand, IMO go for high grade, as in MS65 or better, made from early state dies
though it's unlikely anything in your pocket or change jar will meet those criteria, you can refine your grading skill by looking through those coins, and setting aside the relative best ones
in my experience, the best chance of getting high grade examples is from a fresh, solid date roll, but sadly, even when fresh from the mint, many nickels of the past 20 or so years exhibit huge gashes, as if the edge of another nickel had fallen onto it from a great height; which makes for a challenging search