You can probably just install it straight-up and put the basic roles on the box (CAS, Hub Transport, Mailbox roles)
using the setup wizard. It's pretty easy and doesn't require a lot of effort, but you want to read the recommendations below before you dive in.
My first recommendation, and the most important in my opinion, is to take the time beforehand to configure your Exchange and OS disks appropriately - if you expect *any* kind of email flow above and beyond an email or two every now and again, strongly consider making sure that you physically separate the logs from the mail databases, and keep the OS on a 3rd physical disk or array. You can get away without a 3-disk configuration for a "basic" single mail server, but.... in my experience, don't - it will be the single biggest headache long-term if you do. That's my strong recommendation from experience (I'm a performance consultant for a particular large software company, and Exchange configuration issues almost always come down to failure on initial sizing, with the other big issue being storage that can't keep up to load).
My second recommendation is to
use public SSL certs from a reputable vendor, and don't use an in-house or the included self-signed certs. It's not worth the headache to save a few dollars here. I have seen lots of vendors used here, but use one you're comfortable with and that is part of the main root certs in the OS and browser(s). Digicert and VeriSign are good here, but again, it comes down to comfort and potentially cost. Digicert is one you may hear a lot about for Exchange, as they offer pretty good pricing for SAN certificates specifically for Exchange 201x usage compared to some alternatives.
Third, and probably (post-install) as important as my first recommendation, is to go directly to Exchange 2010
Service Pack 3 if you choose 2010, and then immediately install
Update Rollup 1 for post-SP3. There are some serious fixes in that combo, and it should put you at the latest supported update level for Exchange to boot. On top of a fully-patched 2008R2 or 2012 box, Exchange 2010 makes a good email server choice, but if you don't go with 2013, you've got a decent amount of patching to do before you should put it out there publicly.
Last, test your configuration - Microsoft has set up a site to do just that:
https://www.testexchangeconnectivity.com/
Fix any issues found, and re-test until it all works. You'll be glad you did once you start putting it out on the network and internet, and publishing mailboxes to your users :).
