OK here are a couple list of my "pain, problem, need and buy" keywords.
Some may be dups, don't have time to go through and check.
eliminate cure Pain relief problem lower Relieve prevent alleviate soothe comfort comfortable lower reduce remove Order buy deal bargain sale acquire purchase guarantee guaranteed secret solve correct control solution increase build strengthen fast instant weaken weak strong strong faster quicker smaller big bigger technique tip key aid
Another list I have - some may overlap some words on the list above:
buy
purchase
order
want
how to
way(s) to
now
immediately
cure(s)
resolve
solution(s)
treatment(s)
relief
resolution(s)
alleviate
relieve
remove
rid
get rid of
remedy
training
detect
repair
fix
delete
review(s)
compare
scam
comparison
instruction(s)
book(s)
guide(s)
ebook(s)
manual(s)
direction(s)
manage
tip(s)
technique(s)
secret(s)
better
stronger
faster
quicker
bigger
smaller
fast
quick
big
best
strong
small
less
top
control
deal
help
overcome
prevent
stop
therapy
Also check a thesaurus to get related KWs.
Example Pain - pain - Synonyms from Thesaurus.com
Synonyms: ache, affliction, agony, burn, catch, convulsion, cramp, crick, discomfort, distress, fever, gripe, hurt, illness, injury, irritation, laceration, malady, misery, pang, paroxysm, sickness, smarting, soreness, spasm, sting, stitch, strain, tenderness, throb, throe, tingle, torment, torture, trouble, twinge, wound
Another tip - I like to start with the free KW tool at SEObookhttp://tools.seobook.com/keyword-tools/seobook/ just to start drilling down and narrowing down niches. Mainly because it's so easy to click over to see what the Google, Yahoo or MSN competition is like. Or if you scroll down it will take you to dictionaries, thesaurus and all kinds of other research tools with your KW already added.