In my experience, nobody has ever practiced lesson 1 enough. So here is something to start you off and keep you busy till we meet again. This is primarily for chording instruments, such as guitar, banjo, mandolin, ukelele, piano, etc., but it can be adapted to melody instruments like the fiddle and tin whistle, also.
I call it Chord Pairs and its purpose is to focus your attention on one pair of chords at a time. Using this exercise, you will develop your muscle memory for chords and the ability to switch from one to another in absolutely THE shortest time possible.
To begin, pick a pair of chords. C and G7 will do for guitar, piano, and ukelele players, G and D or D7 for banjo and mandolin. Form the first chord and strum it once (more than one strum is wasted). As soon as you hear it, start moving to the second chord. When you get to it, strum it once and return to the first. Go back and forth for two (2) minutes in a row.
Don't worry about how fast you move from one chord to the other or about how many times you change in that time. Take as much time as you need to make each chord correctly. Be sure to go for two minutes.
Also, as you strum each chord, say its name out loud so you can hear it. It's important that you actually say it out loud because this sets up a biofeedback loop that increases the assimilation rate for your right brain, which ultimately controls your hand.
Match up each chord you know with every other chord and keep a list. Do five chord pairs every time you practice. This should take up ten minutes altogether. Do the same five pairs each day till they get easy or rotate through the list, doing the first five one day and the next five on the next day. It won't matter which way you choose, because each chord pair will reinforce every other one.
Here's an example of how to run the permutations for your list. When you only know two chords, all you have is one pair:
C - G7
As soon as you learn the third chord, you have three pairs:
F - C
F - G7
The fourth chord gives you three more pairs:
Am - C
Am - G7
Am - F
By the time you know 10 chords, you'll have such a long list that you'll never get through it in one practice session. For that reason, I remind you that the purpose of this exercise is to make it easy to switch from one chord to another. Thus, whenever a particular pair reaches the automatic stage, scratch it off the list. Be ruthless!