Can you talk to the stylist on the phone and ask questions prior to a cut, like how they would like you to wear your hair when you come it etc, or maybe they would even let you come in for a consultation before a cut, so you know what to expect and have a chance to opt out if it doesn't sound good to you or whatever?
Regarding your self cutting, if you ever decide to do it yourself again, to avoid triangular look don't cut it straight across, but instead pull all your hair into a ponytail on top of your head, pull it straight up (or bend down so that it's hanging down), and cut off the very ends, first as little as you can, you can always take off more later. This will give nice layers. Best to straighten hair prior to doing this, or at least brush it out. Check youtube, I think there's a video that shows someone doing it.