There's many many opionions on this. It comes down to what you want.
If you think you need or want dual batteries, there are a number of ways to hook 'em up.
You could get one yellow and one red, or 2 yellows, or 2 reds. You could have the stereo & lights to one, and starter to another. Hook them in parallel and have twice the juice, or buy those solid state switches to switch your dual battery mode from one or the other to both.
I like yellow tops, they are just as good at starting as a red and have the deep cycle capability so when your camping and running the laptop off the inverter in the back you don't need to worry about running the battery down.
Do a search here and on google and you'll find hundreds of ways to hook up dual batteries. Think about how you want to run and which batteries to be active running what accessories at what times.
