By accident, I had put <meta name="robots" content="noindex"> into lots of pages on my domain. I have now removed this meta-tag, but how can I get these pages to be re-indexed by Google? Any tip?
I have tried re-submitting my sitemap.xml in Webmaster Tools, but I'm not sure if it works.
Also, if Google will re-index, how long do I have to wait?
Google usually fairly quickly crawls your pages. Inclusion into index is a bit slower, and getting reasonable search rank takes time.
Look at your web server log to confirm that google bot did crawl your pages, you can search for exact page in google and it usually comes up, but to start showing up for relevant terms takes time.
For example if you search for 'dilution calculator' it is unlikely that my page will come up, but if you search for 'bugaco.com dilution calculator' the page on the site is first hit Dilution Calculator - Bugaco
Hope this helps.