Google is hitting too light. Why?

[skuba]

Hi,
I have an amazon affiliate website and google has been hitting frequently, but always only one hit a day.
I don't know why it doesn't go deeper. If Inktomi slurp, the site got hit almost 6.000 times in 2 days.
Someone said that changing my if_modified or last_modified info could help me get more pages crawled.
I read the threads about that subject and still didn't get how do I do that and what should I do. My host company doens't know anyhting about that or how to change those headers.
I would appreciate some help about that or other ideas.
Thanks a lot,
Yan

[plasma]

Check your page with a cachability engine.

[skuba]

I did the thing that shows my header, and I guess there is not modified date:
HTTP/1.1 200 OK
Date: Sat, 11 Oct 2003 04:20:09 GMT
Server: Apache/1.3.28 (Unix) mod_auth_passthrough/1.8 mod_log_bytes/1.2 mod_bwlimited/1.0 PHP/4.3.2 FrontPage/5.0.2.2634 mod_ssl/2.8.15 OpenSSL/0.9.6b
Connection: close
Content-Type: text/html

What should I do to fix it?
Thanks