[ic] ic 4.8.3 foundation - speeding searches

[DB]

I'm kinda new to IC but I've read the docs and done some mailing list 
archive searches. I have my site up and running and am doing some final 
tweaks before opening to the public. I'm using MYSQL and Redhat 7.1 and 
have something like 40,000 records in my products table and maybe 50 
categories.

Searches run pretty fast now, but I want to be sure I'm not overlooking 
something simple that would speed things even more. I have 3 questions:

1) I saw in the docs that a few of the fields in the products table are 
unused in foundation. Would removing those columns altogether help the 
search speed at all?

2) I also saw references in the docs/archives that "indexing" can 
improve search speed. Can someone give me a link or quick 
howto/explanation of indexing? Mostly I'm doing searches of only the 
"comment" field.

3) Which mv_searchtype is best for searches of just the comment field? 
Any other hints also welcome of course.

DB