Any record officially released or reissued in 1999 is eligible, regardless of format, length, label, genre, or original recording date. "Official" here means no bootlegs and no promo-onlys; the idea is to keep it restricted to records that are reasonably possible to legally acquire. Records released in late 1998 are also eligible, within reason; a good rule of thumb is that if it appeared in last year's poll results, then it's not eligible for this year's poll (unless it was re-released).
Please don't censor yourself when choosing your favorite records of the year. There's no standard of "indie-ness" to conform to, and guilty pleasures are perfectly valid. You also shouldn't be afraid to list records you had some part in making; self-promotion is fine if you feel your record belongs in your top 20.
Note that order does not matter in your poll list, nor do you have to submit exactly 20 records; I will simply take the top 20 (or however many there are if fewer) from each list and count one vote per record per poll entry.