Now I mean a real timewaster that was really, really useless. For me it was to use a reciprocal linkeachange program(linkmarket.com).
A buddy and I printed some calendars for a site one time--we were going to give them to visitors, and use them to promote the site at events we went to. Given the content of the site, we went with a "Girls Doing Construction" theme--like the site, no nudity in the calendar, but we thought it would be appealing. All I can say is, if you ever do something like a calendar to hand out, make sure to get a full sample first...we ended up getting rid of most of the calendars, as the women weren't exactly as attractive as they had been in the thumbnails Toonces51
Mine was using Overture for one of my sites. The problem was that I didn't understand my market. I shelled out over $500 for ads and never saw one sale. I've since changed my tactics.
Well, since I didn't track the results for every promotion method I did I can hardly name the worst... However since I never spent any money on it I think nothig I ever tried was totally worthless.
Holding a contest with a relatively high entry barrier, but I didn't realise the prize I was offering was available for free from other, much better-known sources.