Fakie sliders are the easiest, get smooth fakies, lean back, and turn your bars perfectly 90 and hold it solid, pulling back.
Front sliders you have to carve the opposite way you turn your bars, but don't lean that way, stay central. Then quickly turn your bars 90 and lean back but push your bars forward if you get me? Keep your bars perfectly still the same way, despite what people say do not steer - balance.
Only ever do them in wet or ice until you get them dialled, I still only do front sliders in the wet or on concrete parks.
I've never got round to learning powerslides so I can't comment.