I have a new website but how can I outrank much older websites? what would be the best way?
Little can be done untill your new domain gets some time under its belt. After that its the same old seo routine.
how much time on average?
[font=verdana]Make your site better than theirs.
Please read the SEO FAQ or use the [url=http://www.sitepoint.com/forums/search.php]Search facility to find past discussions about how to improve your ranking. Although well-established sites do get an advantage in the ranking system, that doesn’t mean that you can’t do better than them, it just means you have to fight harder. There are no specific techniques.[/font]
Add fresh, unique, keyword rich content to your website. This really helps to rank your webpage higher for the targeted keywords in google. Whereas in bing and yahoo link building mainly took into consideration.
Depend on the domain authority. If that Old website has low domain authority like 30-40 than surely you can compete it within a year or less. Just make sure you are linking your website from quality domains and earn high domain authority rank than the old site.