Square kicks, distorted sugary synths
I'd guess that thirds would be used a lot, because of the connection with hardstyle. Also, never use sampled kicks, always make your own. Headhunterz (I know he's hardstyle but the same principal applies) sometimes spends weeks on his kicks, so don't think you can make a good synth kick in a few hours.
That's about all I know, sorry :/