Taxes : there's are two taxes applicable on most things you buy : the GST (TPS in french) which is the federal sales tax (7% of the bill's total) and the TVQ (in french or PST in english) which is the provincial sales tax (7.5% of the bill's total plus the GST, so the GST is in fact taxed itself). Most prices advertised do not include either taxes (so you have to add it up in your mind). Not all items are taxed, food bought at grocery stores are not taxed (unless you can eat them "on the spot" like chips or candy). If you are a visitor from outside Canada, you can have the GST refunded on certain items but only if they are intended to be used when you return and you have a mimimal purchase of $50 CDN on each receipt (so the GST on meals are not refundable) and on accomodations as long as you stay there less than a month (minimum of $200 CDN). So remember to keep your receipts. The TVQ is only refundable for items which are more than $100 but you can be refunded at the same time as the GST, you only need to fill out one form for both refunds. For more information on GST and TVQ refund and how to get it, try the Revenue Canada web site.

Shopping guide : there's the Smart Shopping Montreal by Sandra Phillips (it has a yellow cover, it's tough to miss) which is great. It has a huge selection of addresses for everything you are looking for and it give a comment on each place.