Where is the FM to learn how to deal with GET parameters and parameters to hooks?

I'd like to have a search form whose results are bookmarkable.

So <form action="/d1/search/items" method="get" > <input type="text" name="code" /> <input type="text" name="name" /> </form>

etc...

so that the resulting url would be /d1/search/items?code=111&name=222 or (?) /d1/search/items/?code=111&name=222

Once I've a search/items hook how can I read extra parameters in the drupalish way?

What if I want to pass parameters to a hook through a url?

eg. I've nameset/dosomething and I want to pass a=7 and b=10 in a similar way as nameset/dosomething/a/7/b/10 or nameset/dosomething/7/10

thx