Audio Systems: Yellow top Battery, automotive relays, long periods of time

Question
I would like to wire a second yellow top battery inthe trunk for my system.  I can't find out how to wire this.  How would i wire a second battery the right way?  Please help me with this.

Answer
well first I would say 2 things, one is that they yellow top batteries are kindof a ripoff and you can get just about as good a battery for $65 at wallmart.  they sell HUGE marine batteries, get the largest one you can.
There are a few ways to hook them up.  basically you can hook the posatives together (one battery to the other) and ground each one to the frame (the factory one is already grounded of course)  you will want a fuse no more than 12" from each battery (one at each end) of the pos. wire you run between them.  Batteries do have a habbit of draining eachother when left for long periods of time but depending on how freqently you drive the car it may not be a problem to hook them up this way.  I have a DelSol with 3 batteries and a jetta with 2 and they are both just simply wired together like this and I never have problems.  I also have a benz with 3 batteries and I used a large bank of automotive relays to isolate them when the car is off reason being I dont drive this car much.  IT is a better way of doing it, to use isolators, but it's alot more work and not always nessesary.
LEt me know what you think.