Google Ranking

Hello, i have just completed a website, and i want to improve its rankings in
google and other engines. I have added key words to the home page relating to
the site, and i have labled the index page with relevant words for the google
robots to see. I was wondering if there is anything else one can do to increase
a sites ranking ?

Also, does anyone know how often the cache of google is cleared and or
refreshed? cause when i search for my site, the old holding page is listed
which says "under construction", and its not now. The holding page was removed
last week

thanks, Simey70