Instructions
Checking out books on antique lace is a great place to start. Books can contain a wealth of information and will allow you to compare your own lace to the pictures in the books.
Examine your lace to determine whether the stitches are closer together or farther apart. Observe the pattern and design.
Look at how the lace was constructed and whether the lace appears to be machine made or handmade. You can tell based on the flaws of the design.
Take the lace to an antiques appraiser. Antiques appraisers are specially trained to know exactly the quality and intricacies of lace. They can best give you an estimate of what your lace is worth as well as a bit of its history.