Several of the tests you can directly prep for. I made flash cards for a few of the tests such as the symbol/number test. I also practiced reciting long strings of random numbers backwards. My memory sucks and I can barely remember an ATC frequency but using techniques I taught myself during practice I was able to reliably spit out 9 digit numbers backwards. I also used Lumosity for general mental agility. No idea if it helped, but as I recall (bad memory...) one or two of the Lumosity tests were pretty similar to the cog tests.