Well, the answer to pretty much all of that is: Depends. Helpful huh?
for who to order FROM, look for a seller with alot of feedback (that number x/x after their name inside the auction) where the first number is equal to or almost equal to the 2nd number. Then if they aren't actually equal, go read the neutral or negetive feedbacks given. Personally if the feedback numbers are like 632/640, I don't usually worry to much, I've worked retail long enough to understand that there are people out there who just aren't going to be satisfied no matter what. But if the feedback is like 12/20 then I'll usually pass up that fish unless he's the only one who displays X feature that I want for breeding. (just a note, 20/20 feedback and I'd probly go ahead & give them a try, but thats a personal call, the higher the number then then higher the number of fish they've sold, so the more satisfied customers they've had...)
For fish shipped from overseas they almost always use a transhipper in the country you're in. Since you're in Canada make sure that seller you're thinking of buying from can ship to Canada (if the listing doesn't say they probly don't, but if you really want the fish you can message them via Aquabid & ask). If they do use a transhipper than your cost from seller to transhipper is usually $5 - $10 plus the cost of the fish, the cost from transshipper to you (at least here in the states!!!) is usually closer to $30+ (check with your local post office to find out how much next day shipping starts at & then add at least $5 onto that to get an estimate). Also you can contact the transhipper directly (most sellers put the transhippers name/email right into the listing) to find out what they charge, there is usually handling & customs fee's as well to be paid that they combine together to give you a total you owe them. If the transhipper is close enough to you you may be able to pick them up from their place of business, otherwise yes you'll need to arrange to have the package shipped to someone such as your mother who can be home to sign for it, here in the states express shipping arrives the next day before noon & the transhipper will usually give me the tracking number so I can be sure. In such case tell your mom to not even open the package, just give it to you as is for you to open and acclimitate the fish when you get off work.
If they do not use a transhipper the cost from the seller to you will vary & you'll almost always have to pick up the fish at the airport ( you may then have to deal with customs agents & fee's as well).
Either method can be perfectly reliable, usually the seller will let you know that they shipped to the transhipper today (or x date in the future), and i usually contact the transhipper personally as soon as the auction closes before the fish are even shipped, with the total number of fish ordered, so I can get the total I will owe them, trust me, the faster you get them out of the transhippers the better, many DO charge storage fees!
Either way can be a little expensive for a single fish, however in most cases you can get anywhere from 6 to 10 fish in a single box (check with the transhipper or the seller, also, if via a transhipper they do NOT have to be all from the same seller to get shipped to you in the same box, just the sellers must all use the same transhipper. However if the seller is shipping to you direct then they all have to be from the same seller), in that case the shipping cost itself doesn't generally vary, just the customs/handling fees will go up for each additional fish.
If you don't have a Paypal account open one, its worth it for buying things online at places such as Aquabid & the like and more major retialers are offering Paypal as a payment option online as well. You can also go ahead & open an Aquabid account right away too, it doesn't cost anything, and that way you'll be prepared. I'd also suggest that you not only open the account, but go ahead & place an order for some plants from Aquabid for your new tank(s) (order as many as you like, if they're all from the same seller most will combine the package into one, less shipping!), this will get you some feedback to your name so that the betta sellers will know you're legit as well!