I'm redesigning a website which will have a new URL format. What's the best way to redirect all the old URLs to the new ones? Is there an automated, fast way to do this?

[PolarisMarketing]

For example, the new URL will be: https://oregonoptimalhealth.com/about_us.html while the old one's were like this: http://www.oregonoptimalhealth.com/home/ooh/smartlist_1/services.html

I have redirect almost 100 old pages to the correct new page. What's the best and easiest way to do this?

[GregFindley.co.uk]

If all 100 are like your example, eg. different /folder/ structure and different page name then unfortunately there's probably not an easy/automated way to generate the list of 301s. Having said that, if there's any patterns for the URLs you could try a rule geneator tool like this one: http://seo-website-designer.com/HtAccess-301-Redirect-Generator