My best advice to you is if you are serious about wanting to work there try to gain report with an employee. They get a bonus for recruiting you and you have a much better shot at an interview if they refer you. They have referral cards, but make sure you've spent a little time with them and they know who you are.
The first round is a group interview. Follow instructions, be on time, come prepared all of the usual things. They do have monthly group interviews even when they aren't actually hiring, but they will still say... we are always hiring great people. That's not really true but they will keep your app if you stand out.
The first interview is honestly more PR than anything. They show you a video of how great they are and tell you about all the reasons why you will love working there so by the end you are willing to jump through flaming hoops to work there.
If they are hiring and your schedule works out (you can work weekends and unload their trucks) they may call you back for another one on one where they can get to know you a little more.