I am preparing to do some web development against a SQL Server 2012 server on a fresh install of win 7 x64 development VM.
What should I install first, visual studio or
Neither - you can install them in any order. While you do get the occasional question about it in various different forums, I have done this and never had an issue.
SQL does have a Visual Studio dependency (formerly) called BIDS, but Visual Studio can install over/around this no problem.
Note that this answer is correct when using the initial SQL 2012 release (as that was the latest edition when this question was asked). Subsequent releases may have changed things. I have made this answer CW to encourage others to edit it as necessary to include info about later versions.