There are a number of ways. First step though, is to be sure you have a problem. To do that, you need meters/gauges or be handy with a VOM or both. Most folks figure out they have an issue when the house battery dies "too soon".
To be clear, the issue is that the alternator/truck battery are about 25' away from your house batteries, as the electron flows. As the current flows from your alternator to the house battery, it loses impetus, or voltage. There is a "Voltage drop". The more current, the more the drop. If the voltage at the alternator starts off at too low a level (as is the case with Toyota's), there isn't enough left to actually charge the house battery when it gets there. The cause is related to the stock wiring as installed by the factory, which uses RV standard 14g or 12g wire. When you try to push 20+Amps through that wire, the voltage drops too much to actually be able to charge your house batteries, and the battery separator disconnects the two batteries = no charging.
Fixes?
1) Thicker wires
2) Manually override the battery separator
3) CTEK DS250 to bump up the voltage at the source
4) Rely on solar to charge the house batteries.
Check out my thread that I created as I was figuring all this out for my Hawk build -
http://www.wanderthewest.com/forum/topic/13230-i-need-more-power-scotty/