New, Green, Uncertain! Need help with trimming stem

[gladyjane]

My windowsill orchid, a Dendrobium burana, from the local Trader Joe's is my talisman of sorts for staying alive after moving into an apartment for the first time. I've killed several plants, at least two orchids, so five months of this feisty plant is doing it for me! Watered it once a week off the tap, and its first stem of 7 flowers is finally spent. Two weeks ago, another stem started to push out, and 7 more buds are about to burst into bloom any day it seems. Do I trim just below the lowest flowering node of the first stem?

Excited that I haven't killed that one yet, I picked up an Oncindium this morning. Any tips to keep this okay will be most welcome.

Thanks!