Also make sure you wear shoes with excellent support! I have high arches, and if I don't wear shoes that support the arches, my feet will crack, too. I also can't wear sandals or anything else that doesn't practically completely encase my foot or else my feet crack, too. I know some people with Lamellar have no problem wearing sandals or going barefoot but I can't. You might want to consider looking at your shoes to see if you can improve those, too. If new shoes are a bit beyond your budget, even just wearing cheap sneakers that you can get for under $20 from someplace like Payless Shoes (if you're in the US) or Wal-Mart would be better than flat shoes or sandals.
Also, when you wear socks, make sure they're mostly if not all cotton. Poly/cotton are not good for your skin. All the ointments people have mentioned are things I've tried in the past, and they are all great. My personal favorite is Bag Balm.
Also, consider getting a big pot or bucket or tub or whatever, filling it with warm water and perhaps a capful of some type of oil like canola oil, peanut oil, almond oil, etc and soaking your feet for a good 10 minutes or more before putting on the ointment and socks.
Exfoliate your feet as much as you can. When I have thick scales on my feet, they often cause the cracks in my feet, and once in a while, the edges of those big scales will even slice my feet. So that's when I soak my feet and keep a pair of nail scissors next to me so that as the scales loosen, I can gently clip them off with the scissors. Nail scissors are the curved kind and I like those because I can get close to the non-scaly skin and not worry about cutting or pinching it. If you soak your feet 2-3 times a week, I bet within a month or more you'll see a big improvement.
I am female, and was born in 1972 with Lamellar Ichthyosis.