Random posts?

Please let me know how i can do this … I have a blog that i’m using as a review site so it will not get updated that often but i want it to appear so, as well as showing returning visitors new options so i would like the index page to show a random selection of posts. i’ve looked through the old posts on the forum about randomising the index page posts and either the plug-ins are incompatable with 2.3.2, code posted is for older versions or the plug-ins do not do quite what i would like.
i’m sure its just a case of putting a randimiser call into the code somewhere but the last time i programmed anything it was made by Sir Clive Sinclair so all help would be welcome.
thanks