i also prefer to buy in person, but there are fewer and fewer LQS. so i buy online. i only buy from sites i know, like connecting threads or quilt in a day or thousands of bolts, etc. they have never let me down for quality. you have to decide what you need. some sites offer fats. i work like this: if i like it, i order 1 yd. if i love it, i order up to 3 yds. if my life will end without it, i order up to 5 yds. if i see something i love for a backing and the price is terrific, i buy 9 yds, for the back and maybe the binding. i buy on spec, so i only order on great sale, preferably clearance. that means i can't always get the amount i want. you have to decide wether or not to take what they have. i make large quilts, but you know what you need in size. many companies will take back if you're not satisfied, but you pay shipping on that.
REMEMBER to watch out for the shipping. if you order only a small amount the shipping can be more than the fabric. that's why i only shop great sales. and when i do, i buy a lot. also, the fabrics are frequently discontinued, so don't count on getting any more later.
look for a sale that offers "no shipping charge" and start there. pm me to let me know how it turns out.