robots.txt will not prevent the page from being indexed. It will only prevent it from being crawled-- which means that if you've made any changes for the better, g can't see them. What you need to do is
#1 set up the redirect
#2 go into gwt and delete the page from the current cache and index. Next time g### tries to crawl the page, it will meet the 301 and it will carry on from there.
That's assuming for the sake of discussion that the redirect approach is the right way to go. Don't look at me; I don't speak SEO.
Putting a meta noindex on the old page won't do any harm-- but won't do any good either, if the redirect is starting right now. And "nofollow" is obviously pointless on your front page-- it would only prevent google from following links away from the page into the rest of your site, which is exactly what you don't want!
bing wmt has a function for "I disown this link categorically and decline to have anything to do with it" but I don't think g### does yet. Unless I blinked and missed something.