if you're a little more tech savvy, http://greyhat-security.com/wep-wpa-cracking-test-your-security
if you're not or you just want the easy way, look for a series of numbers and letters with 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, a, b, c, d, e and f. those are the only sixteen characters that can be in a wep key.