What are your goals?

You can always look on sedo for domains already parked for sale, you would then be able to obtain the earnings of the domains in order to make offers for them that make sense.

My goal is to park them and earn cash.

That's why i ask, which domains will get more cash.

Got answer on other forum that this 3 methods are good:

1. use keyword domains that have high search (not sure about this, someone can confirm?)
2. typo domains like obama.com, you buy obana.com or something like this, this works but im not sure about trademark
3. actual popular domains, like obamaforpresident.com when he was electing or recent chilean earthquake, chileearthquake.com or something like that.

Lets talk about this

I'm not sure you can earn quite a good amount of cash from domain parking, never heard about this. I mean, a few cents there and that's all.