1. Targeted email marketing (cost effective, CPC relevant to your ad CTR and
is easily tweaked by your adcopy, lists target, etc. NOT by $$ bids)
2. PPC (purchased traffic AND more targeted since people are looking for it)
3. SEO - free but can be a pain in the ass BUT worth it.
personally, for me, i test potential campaign by email first (most of the time) or
via PPC and then do both for those that do well. If they do fantastic, then
i have my crew do all of them and in some cases dedicate certain mail servers
as well. On the SEO we do mostly tricky blackhat stuff and link building.
However, some stuff just wont work with email and vice versa...etc..
Then again, thats what tests are for.....test...analyze.....revise....test.....$...
test....analyze....revise.....$$$.....test....analyze....revise.....$$$$$$$$$.....GET THE PICTURE...hehe...my 2.5 cents.