from 1)local yarn brand distributor store; 2)on-line shopping (i.e. WEBS) for good deals; 3)eatern wool fair for good quality, varities and sometimes good deal
Be careful when you do on-line shopping as the color and texture could be very misleading by looking at the picture only. Visit local yarn store as much as you can and get familiar with the brand before you do on-line shopping.