[ikopylov]

1
Root htaccess should be as short as possible and so that there were fewer rules as
Any rules slow down the speed of opening a website.

2
Try to use Redirect and RedirectMatch.
In particular, RewriteRULE load slow down the site

3
Very great importance sequence of rules.

Example
read 1 line, there is a match - execute, no: read a line 2
read 2 line, there is a match - execute, no: read a line 3
etc

RewriteRULE performed primarily from any row

4
Divide your htaccess into several parts

For example:
If you have two or more lines that comply with the rules of redirects in site.com/TAGS/
Create a folder on the server TAGS
And put new htaccess with redirects in this folder

5
Images.
Create a subdomain IMAGE and drag it all the images.
it's make "parallel loading" of images, and accelerate the discovery of page
At the root of the subdomain images.site.com create htaccess with all settings for images

Sorry for my bad english )))