Top/bottom dont really matter Smaller (softer) the cut the faster it will root. If you 'top' your plants then of course you can always root the tips that you remove, don't waste them If you look at the last post in my thread (today) you can see 2 clones I just cut and placed in my usual home made (cut down milk bottle!!) clone rooter
Its no great science, just keep everything clean and keep the cuts warm and moist. 7 to 10 days you will have roots!
The bottom has more Hormones in it and is the easiest to clone and root. the higher you go up the harder and less chance of rooting.
Checl out my album on my signature Clone 101 and clone 101 2