Change the Key of your Warmup/Jam Harp
Last week my tip focused around changing your car/travel harp often... you don't want to become really comfortable with one key of harmonica at the cost of not being able to play the others well.
My students and I tend to grab an A Harmonica as our gut reaction for a key of harp to pickup that's very neutral across its range (not too low or high)... rightfully so, it IS the most common harmonica used, BUT... again, we don't want to become overly dependent on one key of harmonica. Grab the G or Low-F for a lower harp... the D for a mid-high harp... and an F for the high harp.
All students past the one year mark should be spending 1/3 of their practice time applying licks they're learning to the Chorus Form process to build their improvising skills. Make a point while doing this to use different keyed jam tracks each day, this way it's just part of your every-day practice to use different keyed harps (not to mention how good it is to play to different grooves each day).