There are a few articles here and there about hill running. It's best to remember that there are various different types of sessions you can do, all of which are aiming to get you different types of benefits.
Hill repeats are sometimes done i all sorts of different ways. Some people favour hill sprints, which they walk back down from, others steady up and down, others still like to sprint up, jog down. My favourite, as I aim at doing marathons that have hills, is to run up as slowly as necessary, to feel that I'm making a simiular effort to running on the flat, and then muller the downhills.
When you talk about how your feet are striking, going up and down hill: On your way down hill you can actually tell a lot from the sound you are making. If you are hearing a proper thud, then you are probably braking somewhat in order not to lose cohntrol of your descent. This kills the quads!! Try for the rapid turnover. The session that I use which I describe above seems to help me. Find a hill of perhaps 200metres and do repeat descents, once you've warmed up and start with 5 repeats once a week for a few weeks, and then increase to 10.
On uphills try not to push from the toes, as it increases your chances of shin splints.
I always like to warm up properly by doing a mile ot two of relatively flat before and after a decent hill session. Whatever you try increase it gradually. Good luck!