Buy from a store where you know your size already. Use paypal preferably. Check the type of fabric the garment is made from because a computer screen doesn't always make this obvious, same goes for colour. Most importantly, remember you don't look like the models and you can't try this stuff on (some sites even make you pay to return) so be sure you're getting exactly what you want. All that aside, online shopping is great for a bargain, especially eBay.