1) The pattern here are mostly thread and the thread weights used are the same standards today. However, anything that is not worked in thread will be using a yarn that is no longer being manufactured. At Vintage Knits they have compiled an extensive listing of discontinued yarns, arranged by weight of yarn, by brand name, and if known, with fiber content and yardage. This information is a big help in finding a subsitute yarn to work with.

2) The patterns found at lady_n_thread are American but if you get your hands on a pattern that is British/Australian then you will need to use a stitch conversion chart.

3) Very early vintage patterns may have a different interpretation of stitches and the abbreviations of terms may also vary from todays. Crochet Treasures has collected a number of Pre 1930 Crochet Stitch Instructions. [Note: This site appears to not be working. I am researching and hopefully will track down if the information is still on the web.]