Some more methods.
1D6 to determine your modifier, 1 & 2 being -2 and -1 respectively, 3, 4, 5, and 6, being +1, +2, +3, and +4 respectively.
Roll a percentile to determine high or low (ex. 4 = +2 = 14 & 15. High would mean the stat is 15.) For 18s (6), high or low determines if you get a bonus...