Women ... ok, so you married a deadbeat/slob/skirt-chaser/etc. and finally gave him the boot. But WHY did you marry him/move in with him/etc., in the first place?

I know a multitude of women who married men they thought were ok, but who turned out to be lazy or alcoholic or drug-addicted or just deadbeats. They finally unloaded them, but not before damage was done. Did this happen to you? I really am interested in knowing why you married someone like that, and what the warning signs were in retrospect. What sort of advice would you give a young woman to avoid this sort of catastrophy?