i have been finding short, rolling hills lately, and am curious as to what the proper technique is? do i go to a lower gear and slide my butt back further in the seat? do i come out of the saddle?

i have a double chain ring on my bike so i know that doing hills will be a little challenging at first.

i just want to put the least amount of strain and stress on my knees as possible.

also, if i do come out of the saddle, do i keep my weight centered over the pedals, or do i lean a little forward?