Zara fit is on the small side. I size up in their clothes. They are cut more like European clothes, narrower or slimmer overall. In tops, I wear an xs or am sized out of some American brands, but I typically wear a small in Zara. I don't have many bottoms from Zara but those I own are also size S. I would size up in their denim, too, although I haven't really tried it on and don't own any.
Shoe sizing is on European lines -- so if you usually fit EU sizes you will fit their footwear, but it varies a great deal in quality, with some pairs being surprisingly good, and others extremely uncomfortable.
Quality can be iffy. But occasionally you'll find an item there that wears like iron.
I shop a lot at Zara because the clothes tend to fit me off the rack, the styles are current and fun, and I get free delivery and returns, unlike most other places in Canada. I use Zara primarily for style refreshers -- items that make my core wardrobe of classic higher quality items feel current. I like the store for tops, for some footwear (must choose judiciously), the occasional bottom, and jackets.
I send back far more than I order because I don't like the quality or feel of the fabric once I receive the item, or because the fit is off. I far prefer their online shopping experience to the in store one -- the stores can be packed, lineups at change rooms, indifferent staff, messy. The website is clear, easy to use, simple and deliveries are fast and returns a breeze. I've only had one problem with them, once, when a delivery went missing and they dealt with it poorly; I think it may have been down to the individual staff member. Eventually I got it sorted.
If you want to try an item, I would recommend starting with size M and also paying close attention to the cut of the piece; is it one that is likely to flatter you? Tees and knits are easier and more forgiving than tailored pieces in terms of fit.
