To redirect all links to www.example.org to goto www.example.org/new add this to your .htaccess:
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{REQUEST_URI} ^/new/
RewriteRule ^(.*) $1 [L]
RewriteRule ^(.*)$ /new/$1 [L,R=301]
</IfModule>
I'm a bit confused by your question. You subject line seems to ask a different question to the body of the question. But if you don't want search engines to crawl your new site while you working on it add it to robots.txt (though if there is no link on your old site to the new one it should not crawl the new site anyway). And you might want to password protect it as well.
Also for SEO purposes you will not want to break links on the old site once you go live with new site. Use rewrite rules like so:
RewriteRule ^corporateplan$ /corporate-services/corporate-plan [L,R=301]