General SEO advice

Hi,
I have just created dynamic page titles and meta descriptions for SEO.
Firstly, how long will it take google to find the pages and indx them again with these changes? Do I need to resubmit a sitemap to make it happen quicker?
 
Secondly, other than URL rewriting, what else can I do for SEO? How do I target a specific keyword to try to get me higher ranked for it?
 
Thanks for any advice
 
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