"is it all about the keywords or the bid? or maybe the landing page?"
It's a combination of many things including the one you mentioned and more.
"life insurance" would be very expensive and too competitive - unless you ARE a life ins company and have a big budget. It also may be too general and could attract info seekers and lookie loos are aren't ready to buy.
So adding words like
buy life insurance, life insurance
quotes,
best life insurance
rates may be cheaper yet better converting.Of course those are just a couple obvious ones off the top if my head that everyone would be using so still probably fairly expensive and competitive. So pros would drill down even deeper to find more and longer phrases and then also combine with location KW.
Using location keywords "
New York life insurance" may be cheaper
and "
cheap term life insurance
quote New York" may be even cheaper and you would not get as many clicks but they'd be pretty targeted and probably convert better.
KW research is a bit of a science and the pros may put up a life insurance campaign with 1,000 or more long tail key phrases.
I linked to a pretty good beginner article recently I'll try to find it.
Oh got it. It's a sticky in the newbie forum.
Adwords PPC Tutorial - Great 4 Newbies & FREE
There are several other good PPC posts, including in the related posts at bottom of this page.
Hope this helps.