One thing to keep in mind, particularly in doing the first and last assignment, is not jumping to detail too quickly. Several years ago, I did a personal challenge to sculpt something every day, but only for 15-30 minutes. This short time frame did 2 things for me. First, I’d gotten to where I wasn’t using Blender in general as much as I wanted, and so 15-30 minutes was a “doable” amount of time to commit to working on something every day (ie overcoming the “I don’t have time” objection). More importantly, though, it forced me to work on the general forms of the sculpts, because while 15-30 minutes is plenty of time to get in at least the idea of a sculpt, it’s not enough time to spend loads of time on any one detail. Several of my favorite models that I use in testing different things, particularly materials, came from the exercises I did that month.
And I’m a big fan of experimentation (which shouldn’t be a surprise if you remember what I said last week). That month of sculpting gave me lots of opportunities to explore the different tools and features of sculpting that has made my sculpting that I’ve done since be so much better.
Don’t be afraid to try asymmetrical sculpting, either! While it is challenging, you can wind up with more dynamic and interesting sculpts.
(I consider myself a little slow at sculpting… I see some do “speed sculpts” in an hour and get as much detail as it would take me hours of work to get to. Don’t let that deter you… They’ve probably just had more practice!)