Here are 4 kinds of power chords:

|---------------------------|
|---------------------------|
|---------------------------|
|---5------5-----5------7--|
|---5------5-----3------5--|
|---3------------3------3--|

I know they have terms for these, but can't remeber them (theres also probably more forms :o .)

These can be difficult for someone who doesn't have a lot of hand strength, on some songs wheres theres a lot of standard tuning power chord changes my thumb starts aching so I bar with my pinkey instead of the ring while my thumb is over the neck ( you can also individually fret the notes, all up to you.) After you get your strength up, you shouldn't have a problem with them. These are the "easy" chords to play/switch.