Huge problem is fit. Especially pants. So many things can go wrong. Too tight in the thighs, pants run short, pants are tighter than usual in the hips, weird fit in the butt, etc. . .
Feel/quality is a big one for me personally because I have some hangups with textures. If something has a certain feel it makes my skin crawl.
As for suggestions and opinions, I'm usually looking for advice, make sure I'm not committing any faux pas with my choices. For example, when buying some leather shoes I may want something that can be worn with jeans or with slacks if needed. If the sales associate is knowledgeable I will probably go with something I initially was tentative about or didn't consider.
Hope that helps.
The first pair that came were too short, and a bit big at the waist; the company agreed to swap them for a shorter pair (but I had to pay to ship the old pair back to them). I couldn't tell if going to a two-inch-smaller waist would mean an uncomfortably tight waist, so I didn't ask them to send me a pair with a smaller waist. The fit is now at best acceptable.
I could have been more stubborn about it and done more exchanges until I was happier with the fit, but that would have meant more inconvenience - and the expense of shipping them back again. Had I been buying at a shop I could have tried on a whole bunch of pairs of jeans, and I think I'd be happier with the overall fit.
For comparison, I have successfully brought sneakers, t-shirts and sweaters online so I'm no stranger to shopping for clothes online.
What's your main problem? Finding out how it would look on you? How it feels/quality? What are the suggestions and opinions you look for?
Thanks :)