BeginnerQ: Combining a form_for with find() to search mysql

I've looked over the AgileROR section on forms and the secion on
find() but I am still a bit confused. What I want to do it pretty
simple: I've got my inventory listing working and at the top I want
the user to be able to narrow the listing based on a few columns in
the database using a select form. I.E., I have a select pull-down
that lists all of the makes in the :make column in the database (and
doesn't list the same make twice) and the user can select one of the
makes and hit submit, then the user is given the inventory listing
with just those makes. Most of the search related documentation seems
to deal with fulltext search, which is not what I want. Just a select
for :make, :model, :price and :carvantrucksuv -- I know how to
define :choices for :price and :carvantrucksuv in the model. But I
can't seem to get the form or the dynamic list for make and model to
work. (I think I use :action => :create but I'm pretty lost)

I think that might work, I'm going to give it a try. I was going to
try and do it without AJAX, but since it doesn't seem to be spelled
out anywhere else using just a simple form, AJAX is fine. Although
I'll have to figure out something with price constraints form.select.

Crazy thing, I can search it now but AJAX doesn't seem to be working:
I have to enter the text in the box and hit enter. Ah!

Bam! Got it! Just forgot a <%= javascript_include_tag :defaults %>.
It works great. Results like this make me want to continue learning
how to program. Now I've just got to figure out how to combine two or
three of these to narrow the results.

One hitch:

Enter the maximum price: *TEXTBOX*

Code:

conditions = ["price < ?", "%#{@params[:query]}%"] unless
@params[:query].nil?

Doesn't work, I've got the code wrong.